[User] Please transcribe this text

[Assistant] Better than that, right? So let's say, let's say, magically I put a 3 volt battery, 3 volt voltage source, in there. Would that solve the problem? Do you still see a potential problem, at least?


[User] Please transcribe this text

[Assistant] It seems to up, kind of like ostensibly it has solved the problem, right?


[User] Please transcribe this text

[Assistant] If your supply voltage becomes 6 volts, you're messed up. So you can say, well, if the supply is exactly regulated and well defined in your circuit, yeaah, maybe.


[User] Please transcribe this text

[Assistant] But it's not a good design still, because it's sensitive to that.


[User] Please transcribe this text

[Assistant] Right? Because this point is reference to VDD and this point is reference to ground.


[User] Please transcribe this text

[Assistant] Right? This is the way to think about the problem. The problem is that this stage is referenced to ground for this voltage needs to be referenced to this supply, and this needs to be referenced to the top supply, and they can potentially change, and as soon as they start changing, then they can, everything can go haywire, even if you had a three volt or perfect voltage source. So how do we do that? How do we solve this problem? Well, okay, so, AC coupling. So that's an interesting suggestion.


[User] Please transcribe this text

[Assistant] Because an op-amp, one of the important things is that it basically has to have gain at DC to maintain operation and, you know, feedback and things of that sort. So, you can AC couple it, but you basically throw away a big advantage. So we are trying to not, not to do that. We are trying to stay away from it.


[User] Please transcribe this text

[Assistant] Think about architectural changes, not just parametric changes. That will help you.


[User] Please transcribe this text

[Assistant] You know, parametric changes are the final stage of the design. Topology or architecture changes are important. David?


[User] Please transcribe this text

[Assistant] Yeah, exactly. Flip it upside down. Just apply this to a PMOS. Right? So, do it this way.


[User] Please transcribe this text

[Assistant] Connected this way. Now both are reference to VDD. So now if my VDD is 10 volts or 3 volts.


[User] Please transcribe this text

[Assistant] This issue is not gonna appear as long as I choose the sizing of these things properly so that at this, whatever this voltage is gonna be. So it's not gonna be dependent on the supply voltage moving up and down, right? Does it make sense? It's a simple change.


[User] Please transcribe this text

[Assistant] But it's an architectural change, it's a topological change, right? That helps you solve that problem.


[User] Please transcribe this text

[Assistant] Are we having that situation? Are we in a place that out of these two stages, which one is the one that's giving us more gain in principle? Because it's this guy, because it has the n-type GM, right?


[User] Please transcribe this text

[Assistant] But I don't want to have this problem. We don't want to have this problem. How, what do we do? What's the next step? Yes, exactly. Invert the whole thing. How do we invert the whole thing? Let's invert the whole thing. So this guy, this goes up there.


[User] Please transcribe this text

[Assistant] This differential pair becomes a PFAT differential pair.


[User] Please transcribe this text

[Assistant] And then you have an NMOS current mirror.


[User] Please transcribe this text

[Assistant] Which will go, now both of them are referenced to the lower potential. Whatever, be it negative EDD or ground or whatever you have. And then you put it here. Of course, this is not gonna be the way it looks. The way it looks is gonna be a PFAT. And this is gonna be another PFAT.


[User] Please transcribe this text

[Assistant] Right, these are the current sources we are making. Then you need a current mirror reference branch.


[User] Please transcribe this text

[Assistant] And then whatever your IRF is, however you're generating it, something as simple as a resistor or something a lot more sophisticated that will give you temperature and supply and process with independence. Okay. So, now we have some sort of a more complete op-amp, right?


[User] Please transcribe this text

[Assistant] Well, the drive here, this is gonna be, this is basically a GMP.


[User] Please transcribe this text

[Assistant] Of this transistor, right? And then the output resistances are gonna be RO, uhm, P and RON.


[User] Please transcribe this text

[Assistant] And then this is basically gmn2, so the gain of the second stage is going to be gmn2 ro n2 parallel ro p2. Right? So the total gain is the product of these two.


[User] Please transcribe this text

[Assistant] Okay, good question. So you're saying that, okay, how about the output resistance? If I put a load resistor here, this is going to kill it because it's going to be RON2 plus R, parallel ROP2 plus some sort of an RL. And if RL is smaller than those things, it would just be RL.


[User] Please transcribe this text

[Assistant] That's true. This op amp is not intended to drive the way it's drawn. It's not intended to drive a resistive load. This is intended to drive a capacitive load.


[User] Please transcribe this text

[Assistant] So that's absolutely right. Okay, any other questions on this?


[User] Please transcribe this text

[Assistant] Weird cock isle, so, something weird about him. This makes you mean.


[User] Please transcribe this text

[Assistant] Or maybe it's because they remind me of people I know.


[User] Please transcribe this text

[Assistant] Everybody, practice, said Ms. Fender.


[User] Please transcribe this text

[Assistant] Right, if you can define one initial condition or you have one


[User] Please transcribe this text

[Assistant] And let's say this box, you can have an input X or Y, we've had this box view, or you can, sometimes you call it UI and UO for the input and output in general. U can be a voltage or a current.


[User] Please transcribe this text

[Assistant] Now, and then let's imagine that you have one energy storage element. So if you have one energy storage element, what you can do is that you can think of this energy storage element, you can take it out. Let's call it C1.


[User] Please transcribe this text

[Assistant] Right, or it could be equivalently an L1, if it's an, if it's a, or it could be an inductor, right? So this is x and y.


[User] Please transcribe this text

[Assistant] Wherever it's connected, you can connect it that way. And you say, look!


[User] Please transcribe this text

[Assistant] It can be as complex as it can be 5,000 transistors inside this thing.


[User] Please transcribe this text

[Assistant] So it can have all sorts of resistors, it can have all sorts of dependent sources, independent sources,


[User] Please transcribe this text

[Assistant] Let's start determining what the transfer function of this thing would be. Now, like I said, ui and uo can be voltages or currents or things of that sort. So, now,


[User] Please transcribe this text

[Assistant] In general, what is the most complex thing this can be? How many poles and how many zeros this can have?


[User] Please transcribe this text

[Assistant] One pole and one zero, right? In general. The most general form of the transfer function of something like this, H of s,


[User] Please transcribe this text

[Assistant] Over 1 plus b1s, a special form of that general transform. Yeaah, right? There are really, this is the most general it can be. Now you may say, oh it may have no zero.


[User] Please transcribe this text

[Assistant] Right? So, for example, if a1 is 0, that means that the 0 is at infinity.


[User] Please transcribe this text

[Assistant] And if for example instead a zero was zero, what would that tell you about the location of the zero? It's at zero, right? It's a zero at zero.


[User] Please transcribe this text

[Assistant] What you see from this expression is something important actually. How many...


[User] Please transcribe this text

[Assistant] Unknowns are there for any arbitrary network that you need to determine.


[User] Please transcribe this text

[Assistant] Three. For the first order network, right? So there are three numbers that if you knew


[User] Please transcribe this text

[Assistant] So what we are going to develop, what we are going to do now in the next few minutes, is a way of calculating these three and writing this in a more intuitive way.


[User] Please transcribe this text

[Assistant] Rewriting this expression that would give you a way to calculate these three with three low frequency calculations.


[User] Please transcribe this text

[Assistant] We're doing three low frequency calculations to determine these three. Right?


[User] Please transcribe this text

[Assistant] A0, determining A0 by some modification to this network and measure and doing a low frequency calculation.


[User] Please transcribe this text

[Assistant] Yeah, replace a capacitor with an open or inductor with short. Or another way to say the same thing is that set the value of the capacitor to zero or set the value of the inductor to zero.


[User] Please transcribe this text

[Assistant] So what do you do? You, like you said, exactly, the way you do it is basically you open circuit the capacitor, you pretend it's not there, and you determine the transfer function of the circuit. I will do examples for you to see that, right?


[User] Please transcribe this text

[Assistant] So it's going to be a low frequency calculation similar to the calculations we've done so far. So you can calculate that. And whatever that is,


[User] Please transcribe this text

[Assistant] Now, we give this a new name, or a new symbol, because this kind of symbols will help us do it. So this is something, it takes a little bit of getting used to, so let's get used to it. We will call this H superscript 0. Now,


[User] Please transcribe this text

[Assistant] And in general, whatever is in the superscript,


[User] Please transcribe this text

[Assistant] So now, I'm gonna say it and we'll see it many many times in many examples, but if you wanna know what the superscript refers to is this.


[User] Please transcribe this text

[Assistant] If that doesn't make any sense to you now, don't worry, I'll explain it in detail. Because right now what we did is z is zero valued, right? We set this value to zero.


[User] Please transcribe this text

[Assistant] In a first order system, let's say for the capacitor for now, and then we'll talk about the inductor in a second, uhm, let's say you had a capacitor attached to some sort of a linear network.


[User] Please transcribe this text

[Assistant] What determines this thing? What determines where the pole is? Where this B1 is? There's something there, right?


[User] Please transcribe this text

[Assistant] We talk a lot about, what is the one parameter that determines the first order system's response, for example? The time constant, right?


[User] Please transcribe this text

[Assistant] If it's a capacitor, if it's a capacitor, it would be an RC time constant.


[User] Please transcribe this text

[Assistant] Or if it's an inductance, L over R time constant. But it's a time constant, right?


[User] Please transcribe this text

[Assistant] So we know from the first order system analysis that this part of the response, this B1 is the time constant, right? So we know that B1


[User] Please transcribe this text

[Assistant] The resistance. What resistance exactly, right? The resistance that you see across here, across this port. This resistance.


[User] Please transcribe this text

[Assistant] Right? We'll call it R superscript 0, or you could call it R1 superscript 0. Subscript 1, because it's associated with element 1.


[User] Please transcribe this text

[Assistant] But we are, we have only one element for now, so don't, we may drop that R subscript one in your, in your handout, I think I've dropped it, for this part. But again, you can write it as R10 or just R superscript 0. So,


[User] Please transcribe this text

[Assistant] Or you can write it this way. For now. Because you only have one element. If you have more elements, then you have to worry about which one is which. Right?


[User] Please transcribe this text

[Assistant] That resistance, how do you calculate it? What's the mechanism for calculating? It's a port resistance, right? We did a problem set on this, right? You remember earlier on? It basically is


[User] Please transcribe this text

[Assistant] How do you ca- when you calculate it, there's one thing you need to do. You need to null all independent sources. For calculating the port resistance, right? Including your input.


[User] Please transcribe this text

[Assistant] So you null everything, including your input, because that's part of the...


[User] Please transcribe this text

[Assistant] Independent sources that you have. Now, if this input was a voltage source, nulling it would make it short circuit.


[User] Please transcribe this text

[Assistant] If this input was a current source, it would make it an open circuit. And you can see that the time constants will change.


[User] Please transcribe this text

[Assistant] We talked about this, that the poles will change if you switch a current source drive to a voltage source drive. If they don't have a source impedance.


[User] Please transcribe this text

[Assistant] One way to avoid that, for example, would be to, instead, if you have a voltage source drive that is in series with some resistance, let's say, I don't know, X ohms, say 8 ohms, right? You can also have a current source drive


[User] Please transcribe this text

[Assistant] In parallel with 8 ohms, basically the Thevenin or Norton equivalents, and if you have something like this that drives this port, then it wouldn't matter whether it's current or voltage.


[User] Please transcribe this text

[Assistant] But, so that's why this is important. But if you have an ideal stripe just going straight into a port, you have to be careful what you put in there. Anyway, okay, so, let's continue.


[User] Please transcribe this text

[Assistant] The capacitor, right? The only element that can have an S. How does it generate it? So for example, the impedance of a capacitor is, you know, 1 over CS, right? Or its reactance is C1S.


[User] Please transcribe this text

[Assistant] So I can rewrite this, so what I'm, what we are trying to do is to derive H1. So this, these arguments are, arguments for derivation of H, sorry, A1. Which would be H1, uh, tau1, but anyway.


[User] Please transcribe this text

[Assistant] Because it was generated by some sort of a CS. So instead I write it as alpha 11, uhm, C1S.


[User] Please transcribe this text

[Assistant] And so, the same thing for the denominator. Beta 11, it's just one parameter, right? C1S.


[User] Please transcribe this text

[Assistant] So do you agree that it can be written, it should be able, it should be able to write it this way, by that argument? Right?


[User] Please transcribe this text

[Assistant] So what is the value of H of S when S goes to infinity? I'm sorry, when C goes to infinity, not S. C goes to infinity.


[User] Please transcribe this text

[Assistant] So element 1 is being infinite value. It's set to infinity.


[User] Please transcribe this text

[Assistant] From th- the only thing that's unknown here is alpha 11 in terms of- you can define alpha 11 in terms of H1. So you can write it as alpha 11 is R10 or-


[User] Please transcribe this text

[Assistant] Let's write that. H superscript one, R one zero.


[User] Please transcribe this text

[Assistant] How I got the beta 1-1? I looked at, looked back at this. Right? We determined this already, right?


[User] Please transcribe this text

[Assistant] This was b1s. So the denominator is b1s, but b1 is now beta11c1.


[User] Please transcribe this text

[Assistant] So, since the C1 is already there, so what's left of it is basically R1, right? This product is this product, C1 is there, so radar 1, 1 of it should be just R1, 0. Right?


[User] Please transcribe this text

[Assistant] So this is the expression that we'll be using. So now,


[User] Please transcribe this text

[Assistant] You can see that there are three parameters, I mean they're slightly different, they order differently, but there are three parameters that determine the first order system in its entirety. Right?


[User] Please transcribe this text

[Assistant] Now, if it's an inductor, the time constant would be different. So, in the case of an inductor, this would be, uh, basically, for example, L1 over R10. But the rest of the derivation would remain similar. You get to the same point, same result.


[User] Please transcribe this text

[Assistant] Looking at that resistance, if it's an inductor it would be L over that and if it's a capacitor it would be L times that.


[User] Please transcribe this text

[Assistant] Now, you also need to determine these two. These are what we call transfer constants.


[User] Please transcribe this text

[Assistant] But there are two different values, right? One is the transfer function, or the gain, the low frequency gain from this input to that output when this capacitor is open.


[User] Please transcribe this text

[Assistant] That's H0. The other one is the gain from this term, low frequency gain from this input to that output when the capacitor is shorted.


[User] Please transcribe this text

[Assistant] Or infinite value. For the inductor, it would be the opposite. For the inductor, it would be H0 would be the gain from this terminal to that terminal when the inductor is shorted, because that's when it's zero value is shorted.


[User] Please transcribe this text

[Assistant] And it would be the gain from this terminal to that terminal when the inductor is open.


[User] Please transcribe this text

[Assistant] So, you can see that, but just, you manipulate the, the active elements, you either short them or open them, and you get a bunch of different gains, so it becomes three simple calculations.


[User] Please transcribe this text

[Assistant] So you don't have to write the, the, the objective, and this method will allow you to do that, is to never have to write KCL and KVL, or nodal analysis.


[User] Please transcribe this text

[Assistant] Let me see if there are any additional notes that I wanted to make about this.


[User] Please transcribe this text

[Assistant] Let's do a few examples of this thing to see if it actually, how it works.


[User] Please transcribe this text

[Assistant] So again, since this is quite important, I will repeat it down here.


[User] Please transcribe this text

[Assistant] Let's do first example. Let's pick a very simple example. Some basic example that we know exactly how they are supposed to operate. So, example one.


[User] Please transcribe this text

[Assistant] Let's do a basic RC circuit, first order RC, with a voltage source input. So this is V in, and this is V out.


[User] Please transcribe this text

[Assistant] This is C, this is R. Let's call it C1. Let's call it R1. Or R.


[User] Please transcribe this text

[Assistant] Okay? We know the transfer function of this thing, right? We all do, I suppose. But okay, let's find out what those parameters are. So, what is H0?


[User] Please transcribe this text

[Assistant] How do we determine H0? We zero value elements, basically all elements.


[User] Please transcribe this text

[Assistant] And look at what you get from the input. So if this is zero value, meaning the capacitor is open circuited, what's the relationship between V out and V in?


[User] Please transcribe this text

[Assistant] There will be no current flowing through this resistor, so there will be no voltage drop across this, so this voltage has to be the same as that voltage, right?


[User] Please transcribe this text

[Assistant] Knalling a voltage source does what? Short circuits? So you have this resistor R to ground. So what do you see looking into here? You see R between these two.


[User] Please transcribe this text

[Assistant] So, and then you have to multiply that, so R, C1. Right? What is H1?


[User] Please transcribe this text

[Assistant] short-circuited. If I short-circuit the capacitor across here, what is my Vout to Vin ratio? Well, Vout is gonna be zero, so Vout to Vin ratio is gonna be, uh,


[User] Please transcribe this text

[Assistant] So what does it generate if I plug it into that equation? So let's say h of s would become 1, the second term is 0, over 1 plus rc1s. Which is the transfer function of that.


[User] Please transcribe this text

[Assistant] Let me put it down here. Give myself more room.


[User] Please transcribe this text

[Assistant] Well, we can calculate it using the same method, right? So what is H0?


[User] Please transcribe this text

[Assistant] But how do we evaluate it? When we set the value of the capacitor to zero, right? We open circuit it.


[User] Please transcribe this text

[Assistant] So it becomes open circuit. So what is the V out to V in ratio here?


[User] Please transcribe this text

[Assistant] Null all, remove the capacitor, of course, we look at where it's connected. All zero value, everything is zero valued now. Now, and null the independent source.


[User] Please transcribe this text

[Assistant] So what, what do you see, if you know the independent source? What is the resistance you will see? If you know the independent source, you've shorted these two. So these two resistors will be in parallel. Right? So what do you see? rA parallel rB.


[User] Please transcribe this text

[Assistant] Which is basically, you can also write as rA rB over rA plus rB c1. This is the preferred form.


[User] Please transcribe this text

[Assistant] But sometimes if you, you will see that if you need to do some algebraic manipulations, it may simplify if you expand it. But generally if you don't have any good reason to do it, just I will keep it in this form.


[User] Please transcribe this text

[Assistant] Infinite value element number one, because it's in the superscript, right? So when I infinite value c1, I've shorted it. What happens? What is the input and output are? Shorter to each other. So what is that ratio? One.


[User] Please transcribe this text

[Assistant] The good news about this method is that actually as you start short-circuiting stuff, things become simpler to calculate. Often. Because a lot of things are just like removed. They're being short-circuited across.


[User] Please transcribe this text

[Assistant] So, what do you see there? So let's let's calculate the h of s. So,


[User] Please transcribe this text

[Assistant] If we factor this term out, which is this term,


[User] Please transcribe this text

[Assistant] And in the denominator, what do you get? You get 1 plus rA parallel rB C1S.


[User] Please transcribe this text

[Assistant] So this is a useful form because the right hand side of it goes to 1 at 0 frequency.


[User] Please transcribe this text

[Assistant] Right? It shows you the zero frequency, the frequency of the zero and the frequency of the pole and the low frequency gain.


[User] Please transcribe this text

[Assistant] So it works nicely for these kind of simplified resistive networks and all those things. Of course it works for other things too. But let me just do one more resistive network.


[User] Please transcribe this text

[Assistant] Let's do one in an inductor, just to get comfortable with those.


[User] Please transcribe this text

[Assistant] Uhm, so, example three. Uhm, let's say you have one, let's do one with an inductor.


[User] Please transcribe this text

[Assistant] R, L, let's say this is your V out.


[User] Please transcribe this text

[Assistant] It's a short circuit. So what do you get? You have short circuit at the output to input, right? I mean, no, to ground, not to input, to ground. Which basically gives you what?


[User] Please transcribe this text

[Assistant] Zero. So the output to input ratio is going to be zero. H0 is zero. Now, what is the tau?


[User] Please transcribe this text

[Assistant] What is the time cost? So, null all independent sources.


[User] Please transcribe this text

[Assistant] And look what you see from looking here. If you know all the independent sources, what do you see? This is short circuited, you're looking across here, you see r. So what is the time constant? L over r, right?


[User] Please transcribe this text

[Assistant] Open. So, what is the transfer function if this is open? Voltage, this voltage to that voltage if this is open?


[User] Please transcribe this text

[Assistant] Or a zero at zero and a pole at whatever frequency, right? And its transfer function looks like this. So I didn't do the transfer function, we didn't do the transfer function for this, right? The transfer function looks like that. This is basically, uhm, r over, or one over tau.


[User] Please transcribe this text

[Assistant] Right? So it goes really from H0 to H1.


[User] Please transcribe this text

[Assistant] If you look at it here, it's also going from H0, which is 0, to H1, which is 1.


[User] Please transcribe this text

[Assistant] The Bode plot goes from H0 to H1. For this first order one.


[User] Please transcribe this text

[Assistant] And for this one, of course, you had, I forgot to do all of these, but here. So basically you have a single pole, so you can actually, what you're doing is that, so this is a pole.


[User] Please transcribe this text

[Assistant] And you just pull, the frequency is basically 1 over tau. The angular frequency is 1 over tau.


[User] Please transcribe this text

[Assistant] If you want, it makes it easier to manipulate. If the notion of an inverse pole and an inverse zero bothers you, you can think about it as a pole here and a zero at zero frequency. Which analog axis will appear at negative infinity. Okay?


[User] Please transcribe this text

[Assistant] Any questions so far? Are these clear?


[User] Please transcribe this text

[Assistant] What do you think will happen, uhm, beyond that? I mean, just like, at a higher number of poles and zeros.


[User] Please transcribe this text

[Assistant] Well, you have a superposition of sources. We don't have superposition of components. Right? This is actually a very good point of discussion.


[User] Please transcribe this text

[Assistant] There is no reason for components to have superpositions. And actually they don't. So we'll have to see what happens to them. Superposition applies to stimuli, not elements. It's something to think about.


[User] Please transcribe this text

[Assistant] Alright, so let's do a transistor one. Let's do a basic one based on a transistor and we'll expand it. So what we have here is a, uh, uhm, let's do a simple, let's do a simple one first. Let's say you have a, uh, common emitter.


[User] Please transcribe this text

[Assistant] And you have an R1, the source resistance, R1. And then you have a source voltage, Vin. And then let's say you only worry about a Cpi. So let's say you have, right now, because, well, because you only know how to do first order so far.


[User] Please transcribe this text

[Assistant] Let's just worry about one element. We'll see, we'll add those other ones. And see how this, then we'll learn how to do second order. We'll do that. But let's worry about that now. So this is CPy.


[User] Please transcribe this text

[Assistant] Well, we can always draw the small signal model. For this one, we know, we said that when your emitter or your source is


[User] Please transcribe this text

[Assistant] Grounded, the pi model works better. It makes it easier. I mean, again, this is a rule of thumb. You're welcome to use the T model or pi model, whatever you want. So if you look at that, you have an r pi here, you have a v in, and then you have an r1, and then what you have here on the other side, you have the gmv pi. Let's forget about r0. If you had an r0, you could absorb it into r2.


[User] Please transcribe this text

[Assistant] So that's the model, right? And where's the capacitor? The capacitor's sitting here. C Pi.


[User] Please transcribe this text

[Assistant] Okay, let's find out what the, uhm, effect of CPy is.


[User] Please transcribe this text

[Assistant] So we need to find the transfer function for this, right? So there again are three calculations. The three calculations. So what is H0?


[User] Please transcribe this text

[Assistant] Well, H0 is the value when the capacitance is 0, C1, C1, C Pi in this case, is, uh, 0, right?


[User] Please transcribe this text

[Assistant] So if it's zero, basically it's one of those basic low frequency calculations that we have. What is the game?


[User] Please transcribe this text

[Assistant] Well, the gain is the voltage gain from here to there, and the voltage gain from here to there, right? The voltage gain from here to there is what?


[User] Please transcribe this text

[Assistant] What if, what if, what is the effect of the, so what's the time cost?


[User] Please transcribe this text

[Assistant] And see what is the resistance seen by the capacitor, where the capacitor is connected. What do you see when you do that?


[User] Please transcribe this text

[Assistant] Yeah, you see the parallel combination of these two resistors, right? Because if you null this,


[User] Please transcribe this text

[Assistant] Right? So this is going to be r1 parallel r pi times c pi.


[User] Please transcribe this text

[Assistant] So, done, we're done. In fact, as far as I'm concerned,


[User] Please transcribe this text

[Assistant] And we know H0 is this, and Tau, this is Tau, whatever, is that.


[User] Please transcribe this text

[Assistant] Instead of like, writing these massive expressions, useless massive expressions.


[User] Please transcribe this text

[Assistant] The whole point is to write it in a simple enough form that we can see what the insight is.


[User] Please transcribe this text

[Assistant] We don't want to kind of tie our hands behind ourselves and shackle our feet just so we can go and try to do something.


[User] Please transcribe this text

[Assistant] Perhaps some simple forms that we can see. So yes, it's a first order response. It has one pole and no zero. Or zero at infinity. We call it no zero, right?


[User] Please transcribe this text

[Assistant] Can you tell me, can we come up, so this is the last thing we're going to do for today, but just, can you give me an example, and we'll do a lot more examples of this next time, next lecture, but uhm, can you give me a simple way to find out if I have a zero or not? Can you define a simple test?


[User] Please transcribe this text

[Assistant] Of whether or not there's a zero in the transfer function of at least the first order system. We'll see the generalized test too, later on.


[User] Please transcribe this text

[Assistant] Okay, that you can, well, if there's a capacitor, you can short circuit.


[User] Please transcribe this text

[Assistant] You, you have an L, so if you didn't have this, you had just that, right? Now if you short circuit this capacitor, you have a non-zero transfer constant.


[User] Please transcribe this text

[Assistant] If you have a non-zero transfer constant for an element that's short-circuited, or infinite value more accurately, but for a capacitor it would be short-circuited, for an inductor that's open-circuited, then that's a test that you have a zero. In fact, you can even tell what the


[User] Please transcribe this text

[Assistant] Which half plane zero is in? If it's a left half plane or right half plane zero.


[User] Please transcribe this text

[Assistant] What's that, what's the test for that? Divide the test from looking at that equation.


[User] Please transcribe this text

[Assistant] H1 is positive or negative, right? If H1 is positive, it's a left half plane.


[User] Please transcribe this text

[Assistant] It's a negative zero. If H1 is positive, negative, it's a right half play, right? How do we determine that?


[User] Please transcribe this text

[Assistant] So it's the sign of this thing that matters. So,


[User] Please transcribe this text

[Assistant] It's a right half-plane zero, and if it doesn't, it's a left half-plane zero. So is this a left half-plane zero or a right half-plane zero?


[User] Please transcribe this text

[Assistant] If I short circuit this, would it, would the gain be negative or positive now? Positive, right? Because it just goes, signal goes straight through.


[User] Please transcribe this text

[Assistant] Journey to the West, Chapter 97, Bajie and the Monster.


[User] Please transcribe this text

[Assistant] Bajie raised his rake and swung as the monster approached. The demons rushed toward the cape from all sides.


[User] Please transcribe this text

[Assistant] He spun around and knocked over two demons with his Rake. The monster threw a punch. Bajie blocked the punch with his Rake.


[User] Please transcribe this text

[Assistant] The pig muttered. He slammed the rake down on another demon.


[User] Please transcribe this text

[Assistant] Bajie thrust his rake toward him, still complaining about Wukong.


[User] Please transcribe this text

[Assistant] Asked Bajie suspiciously. The monster licked his lips.


[User] Please transcribe this text

[Assistant] Bajie's eyes burned with fury. He turned to the Tang monk.


[User] Please transcribe this text

[Assistant] Instantly the monkey stopped laughing. He jumped to his feet.


[User] Please transcribe this text

[Assistant] I have a plan to lure the spirits away from the monk!


[User] Please transcribe this text

[Assistant] When he was done speaking, the demon folded his arms.


[User] Please transcribe this text

[Assistant] A big smile spread across the monster's face.


[User] Please transcribe this text

[Assistant] So before the break, what we did, we looked at some variations of op-amps in MOSFETs. And just for us to get a better sense of the differences in trade-offs and how things would be slightly different or similar in, uh,


[User] Please transcribe this text

[Assistant] Bipolar transistors will try to make a bipolar amplifier.


[User] Please transcribe this text

[Assistant] So let's set some sort of specs. So we're going to set a spec of let's say we want a voltage gain of greater than a million.


[User] Please transcribe this text

[Assistant] So you wanna have a voltage gain that's greater than a million. We want to have an R in.


[User] Please transcribe this text

[Assistant] Right, the input resistance, the differential input resistance. You want, you have an RL, let's say we have a load resistance of 50 ohms.


[User] Please transcribe this text

[Assistant] So let's say we want to be able to drive a 50 ohm load at least, or higher, 50 ohm or higher.


[User] Please transcribe this text

[Assistant] The early voltage of the NFET, let's say, sorry, NPN is going to be 100 volts and the early voltage of the PNP is going to be, let's say, 50 volts.


[User] Please transcribe this text

[Assistant] Again, these parameters don't exactly matter. I mean, they matter, they do determine the parameters, but the key takeaway from this is that


[User] Please transcribe this text

[Assistant] So, what's the simplest thing? We are looking for something with differential input and a single-ended output that would


[User] Please transcribe this text

[Assistant] Negative VCC, let's say, and let's say this is the positive supply.


[User] Please transcribe this text

[Assistant] We'll deal with the current source later, but let's start with the current source. We have something like this.


[User] Please transcribe this text

[Assistant] The output voltage. And we have a load resistor. I'm gonna put my load resistor here. RL, that's 50 ohms. So let's just do this.


[User] Please transcribe this text

[Assistant] Let's see what we need to do to get some of these basic parameters. We want an input impedance of 50 kilo ohms minimum, right? 50 kilo ohms. So what is the input impedance of this stage? In general.


[User] Please transcribe this text

[Assistant] What is the, what do you see looking into? Think about the differential, the half-circuit equivalent, right? Half-circuit equivalent is a common source, or I'm sorry, common emitter. And you look into the base, what do you see?


[User] Please transcribe this text

[Assistant] R pi. So you'll see two of them. You'll see two R pi. So the input resistance is two R pi. Right? So Rn.


[User] Please transcribe this text

[Assistant] So if I want this to be 50 kiloohms, that tells me something about the IC. Right?


[User] Please transcribe this text

[Assistant] The collector current. This is 200, so this is 50 kilo ohms divided by 200 times 25 millivolts. Right? So you get 200, uh, sorry.


[User] Please transcribe this text

[Assistant] So we want this 50 to be 50 kilo-olps, 50 kilo-olps, divided by 200, 2 V, times 25 millivolts, uh,


[User] Please transcribe this text

[Assistant] Calculate the opposite of that. So it's basically going to be, uh,


[User] Please transcribe this text

[Assistant] Five by five is just one, so it's basically it's going to be 100 microamps. That's the current that, that's the maximum current I can have if I use this stage. In each transistor.


[User] Please transcribe this text

[Assistant] So if I put my tail current at 200 microamps, I will be at exactly 50 kilo ohms. But that's not good design, right? You've left zero margin.


[User] Please transcribe this text

[Assistant] Uh, okay. So, then that determines my GM. Because I know, in the balanced case, what my GM is. Because now each transistor is carrying 50 milliamps, 50, I was gonna say 50 microamps. And my GM is gonna be what? At 1 milliamp, it's 40 millisiemens. So at 100 microamps, it's gonna be 4 millisiemens. And at 50 microamps, it's gonna be 2 millisiemens. Right? So this is gonna be 2 millisiemens. GM. The GMN is 2 millisiemens.


[User] Please transcribe this text

[Assistant] From a half circuit perspective, looking down here, what do I see? I see the RON. At 50 microamps, what is RON? It's 100 volts divided by 50 microamps, right?


[User] Please transcribe this text

[Assistant] I have 50 microamps, early voltage is half of that, I see 1 megaohm because early voltage of the PP we said is half of that of the N. So what is the gain of this stage?


[User] Please transcribe this text

[Assistant] So, 2 millisiemens times 50 ohms is .1. It's a good 1 to 10 attenuator.


[User] Please transcribe this text

[Assistant] So, yeah, but if that thing was not there, what's the gain? You had it. It's just basically, it's just like something like, a little bit over a thousand.


[User] Please transcribe this text

[Assistant] Completely, that completely dictates the game. Because that completely dictates the output resistance.


[User] Please transcribe this text

[Assistant] Right? Because you're reliant, in these stages you're reliant on the high output impedances. And then you just kill this by putting a low impedance in parallel with it.


[User] Please transcribe this text

[Assistant] Okay, so, so, we have a problem there, right? We have to do something about it. So let's say we wanted to use what we have right now and make that work. What do we need to do next to make that work? Uhm, to get that gain up.


[User] Please transcribe this text

[Assistant] What do we do? Well, if we wanted to increase the gain of this stage, what do we do to it?


[User] Please transcribe this text

[Assistant] So you have a cascode current mirror, and then you will do also a cascode


[User] Please transcribe this text

[Assistant] Okay, so now, now what do we get? What's the output resistance? Because this was 2 mega ohms, right? So with cascode, what do I get maximum? Beta R0, right?


[User] Please transcribe this text

[Assistant] This is basically you're pushing the limits of your simplified model. What I usually say is that any optimizer


[User] Please transcribe this text

[Assistant] Because your model is limited. So anyway, you could, even if you could get these numbers, what's the gain going to be? Even if you could get something like 50 mega ohms. Let's say,


[User] Please transcribe this text

[Assistant] If you had 30 mega ohms of total load resistance and you had tons of buffers here between them,


[User] Please transcribe this text

[Assistant] What would your gain be? It's like 2 millisiemens times, uhm, 30 mega ohms. It's 600,000, right? It's still not at a million.


[User] Please transcribe this text

[Assistant] And by the way, this is actually, I made a mistake here. What was the mistake I made? What is the output resistance looking up here? Parametrically.


[User] Please transcribe this text

[Assistant] Right? You remember we talked about this, this kind of thing. So this is $8 over 2, so this is actually 25 mega ohms.


[User] Please transcribe this text

[Assistant] So, 25 mega ohms, so it's less than that, even like, so it's like around 300,000 for, even according to the simplified calculation. Right?


[User] Please transcribe this text

[Assistant] So there's no way you can get to that kind of game with a single stage. So what do we do? We have to introduce a second game stage, right?


[User] Please transcribe this text

[Assistant] Let's say you want to run it off of this, this kind of stage, this kind of amplifier. So let's say, oh yeaah, whatever I get from this, it's gonna be pretty large, but


[User] Please transcribe this text

[Assistant] It's, uh, may not be exact at 400,000, but it's gonna be still pretty large.


[User] Please transcribe this text

[Assistant] So, I need to kind of like bring it now to a second game stage, right? What kind of stage should we use, do you think?


[User] Please transcribe this text

[Assistant] Or common emitter or cascode, right? Cascode is a common emitter followed by common base, right, in bipolar.


[User] Please transcribe this text

[Assistant] And of course, now we know that it has to be referenced to VDD. Because if I reference it to ground, then I have this side that's referenced high.


[User] Please transcribe this text

[Assistant] And this side that's reference to the top supply, and if I put a common, for example, if I were to do a common emitter like that, and hook it up there,


[User] Please transcribe this text

[Assistant] You have the similar problem as we had in the mass hour times. This is reference to ground, so this is going to be whatever, or whatever the lowest supply is, negative VCC. So the lowest potential plus VBE on, this would be 0.7 volt above that.


[User] Please transcribe this text

[Assistant] And this point we know, it's gonna be roughly when the inputs balance and the currents are equal, this is gonna be roughly 2 VBEs, 1 VBE on, 2 VBE on, below VCC.


[User] Please transcribe this text

[Assistant] This is going to be 5 minus 1.4 volts, whatever that is, 3.6 volts. And then this is going to be at, uhm,


[User] Please transcribe this text

[Assistant] Negative five plus point seven, so it's going to be negative four point three volts.


[User] Please transcribe this text

[Assistant] So you connect them, you create some pathway for just free diodes and series between supply and ground, which is not a good thing.


[User] Please transcribe this text

[Assistant] So you have to do a reference to VDD. So, and then you can basically have some sort of a load for it, right? We'll talk about that load later. Okay, so can I just plug this here?


[User] Please transcribe this text

[Assistant] Despite the fact that we tried to reference it to the right supply, at least we solved that problem. So what's the next problem? What kind of problems are we introducing? Yes?


[User] Please transcribe this text

[Assistant] Yeah, the input resistance is going to basically destroy everything. So let's say if that was running at 1 milliamp, what would the input resistance be? It would be 2.5 kilo ohms. So putting 2.5 kilo ohms in parallel with, uhm,


[User] Please transcribe this text

[Assistant] The gain of that first stage would become what? 2 millisiemens times 2.5 kilo ohms, that's going to be a game of 5.


[User] Please transcribe this text

[Assistant] That's, that's one problem. So we have to deal with that. There's a second problem. There's still a problem with DC.


[User] Please transcribe this text

[Assistant] Yeah, the base current of this guy will be provided through part of this branch. So some of the current will come out of here as long as it's not excessive.


[User] Please transcribe this text

[Assistant] So we can kill two birds with one stone there, right? We can put a follower.


[User] Please transcribe this text

[Assistant] So you want something that will follow this. Now,


[User] Please transcribe this text

[Assistant] So, yeaah, I'm going two VBEs down from VDD, VCC.


[User] Please transcribe this text

[Assistant] Then I'm going 1 VBE up here, so I'm 1 VBE below VCC, which is the right value roughly to be around this guy. So from a DC perspective, I'm good with this.


[User] Please transcribe this text

[Assistant] So what is the impedance looking into here? We said it was, let's say, if we want to keep this at 1 milliamp, right? This was 2.5 kilo ohms, or pi, right?


[User] Please transcribe this text

[Assistant] Beta times whatever you have in the emitter, right? Which is r pi plus r m plus r o of that transistor.


[User] Please transcribe this text

[Assistant] So it's basically beta r pi plus r m. Because r o is going to be much larger than that. And r pi is beta times larger than r m. So it's pretty much beta r for r pi.


[User] Please transcribe this text

[Assistant] Roughly, beta or pi, which is going to be 250, well, actually, yeah, 250, that's right, 250, uh, kilo ohms.


[User] Please transcribe this text

[Assistant] And if I'm trying to get a gain of a million, roughly I should get about a gain of a thousand per stage.


[User] Please transcribe this text

[Assistant] You may say, okay, I can try to get more gain out of my second stage, et cetera, et cetera. You can do that, but just, yea, okay. But, you may try that.


[User] Please transcribe this text

[Assistant] If you're really not trying to kill yourself. Or let's say I wanted to get at least a gain of a thousand from the first stage. What do we need to do?


[User] Please transcribe this text

[Assistant] Double that input resistance or output resistance, yeaah. How do we do that? Can you think of a way of increasing that input resistance even more?


[User] Please transcribe this text

[Assistant] Good, you're thinking topologically, architecturally, not parametrically.


[User] Please transcribe this text

[Assistant] I mean, not, not, sometimes you have to think parametrically too. It's just like, great. So that's one way. There's other, there are other ways. You can, for example, you can say, oh, I would run this at a larger, at a smaller current. Right?


[User] Please transcribe this text

[Assistant] If I make this, like for example, instead of running it at 1 milliamp, I run it at half a milliamp, this would become 5 kiloohms, right?


[User] Please transcribe this text

[Assistant] But let's as an exercise, let's just go and try to say, okay, I want to add more followers. I want to kind of, I don't want to be barely there. I want to be, I want to go above and beyond in terms of what I'm asked. And by the way, that's not necessarily always a good thing.


[User] Please transcribe this text

[Assistant] Because what happens is that in the process you will compromise some other things. So,


[User] Please transcribe this text

[Assistant] To get that DC problem, uh, still resolved.


[User] Please transcribe this text

[Assistant] I see some puzzled looks under the faces, right? Neither one would do it, right?


[User] Please transcribe this text

[Assistant] So let's say I really had to increase this input impedance. What would I do? And parametrically I can't do it for other reasons, let's say.


[User] Please transcribe this text

[Assistant] Speed and drive capability of the second stage. I can't go below that 2.5 kilo ohm.


[User] Please transcribe this text

[Assistant] It may be actually even lower than that in practice. Uh, because of the currents I have to bias it at. What would I do? Yes. True followers, excellent. How would that solve the problem?


[User] Please transcribe this text

[Assistant] Right, so use an n-type follower followed by a p-type follower. Very good.


[User] Please transcribe this text

[Assistant] Right? So now, your input resistance is gonna be huge. Right? Because you get another beta here and another beta here.


[User] Please transcribe this text

[Assistant] Now, what is the impedance seen looking through here? Looking...


[User] Please transcribe this text

[Assistant] Seen out, looking out of the emitter of the transistor.


[User] Please transcribe this text

[Assistant] Right, the 250 parallel with whatever this guy presents, right?


[User] Please transcribe this text

[Assistant] So now if you are 250 kilolms, you have to start thinking about ROs. Depending on what the current is.


[User] Please transcribe this text

[Assistant] Right, so let's say this is running at, I don't know, 100 microamps.


[User] Please transcribe this text

[Assistant] So if it's 100 microamps, and it's made out of a bipolar transistor, NPN,


[User] Please transcribe this text

[Assistant] So let's say this is one mega, looking down here, you see one mega ohm. So what do you see here? You see this in parallel with that.


[User] Please transcribe this text

[Assistant] And then, therefore this, according to our basic calculations, is going to be beta times that. So now you're getting into the crazy mega ohms, like tens of mega ohms. Which basically becomes suspect. Numbers.


[User] Please transcribe this text

[Assistant] Well, it's the output resistance, even if this one, let's say this one is at 100 microamps, and this is a p-type, so now this is going to be 500 kiloohms.


[User] Please transcribe this text

[Assistant] Right? So you see 500 kilo ohms in parallel with 20 mega ohms. What do you see?


[User] Please transcribe this text

[Assistant] Still 500 kilo ohms. So looking out here, you see 500.


[User] Please transcribe this text

[Assistant] Oh, by the way, uh, yeah, sorry, yeah, times 100, so you get 50 megaohms. Again, another suspect number.


[User] Please transcribe this text

[Assistant] So now they're in good company. They're all in the same kind of group of people. Right? Or impedances. They're of the same cloth. Anyway, so you're, this is, now it's high. As high as these guys could be anyway.


[User] Please transcribe this text

[Assistant] Limited by the leakage and all those things. So it's not going to be as high as that, but it's going to be high.


[User] Please transcribe this text

[Assistant] It's gonna be like, you're talking about, at 1 milliamp, you're talking about 100 kilo ohms or 50 kilo ohms, things of that sort. And then you put a 50 ohm in parallel with that, that's gone. So we need more buffering, obviously.


[User] Please transcribe this text

[Assistant] So we need more buffering, but also we need something else. We have to be careful about, and this is an important point that sometimes is not realized, or emphasized sufficiently.


[User] Please transcribe this text

[Assistant] This should be able to swing reasonably well, reasonably close, I mean not exactly, to VDD and negative VCC or negative VCC, right? It needs to have some decent swing here.


[User] Please transcribe this text

[Assistant] Remember, you have two gain stages. This is, let's say, we are gonna get a gain of around a thousand or so from here. From this, this is our second gain stage, right? This is our first gain stage.


[User] Please transcribe this text

[Assistant] So the swing from this point back is very small.


[User] Please transcribe this text

[Assistant] As long as the op-amp is operating in proper range of region. That's why we don't really kill ourselves too much about trying to make this swing range very large here.


[User] Please transcribe this text

[Assistant] Which basically maintains the output in the linear operation range. It doesn't rail, they call it railing. It's going all the way to VCC or negative VCC.


[User] Please transcribe this text

[Assistant] But, at the same time, it means that whatever we do from this point on, has to be able to sustain a pretty large swing. Because that was our last game stage.


[User] Please transcribe this text

[Assistant] Can we just put some of these like, uh, let's say, can I, can I put a, can I just copy and paste Ctrl C, Ctrl V of this here?


[User] Please transcribe this text

[Assistant] What would happen? Let's say I just make a copy of exactly this branch and put it here and hook it up to this. Do you see problems?


[User] Please transcribe this text

[Assistant] Well, they have to worry about the impedances and all those, and we'll worry about that in a few minutes. In a minute or two. But just, there's another problem.


[User] Please transcribe this text

[Assistant] How about the swing range? What's the output range? If I take that, what's the highest it can go? Let's say. Does it have any limitations in terms of how high it can go?


[User] Please transcribe this text

[Assistant] Yeah, I mean it can go up to some point, but it will be limited by VBE or something like that, whatever limits that, but that's okay, that's acceptable. How about, how low can it go? What's the lowest it can go?


[User] Please transcribe this text

[Assistant] But the maximum current that this stage can sink is what? 100 microamps, right? 100 microamps out of a 50 ohm. What's the voltage?


[User] Please transcribe this text

[Assistant] So it can go only, it can go negative if I take that, if I copy this stage verb exactly as it is and put it here. It can only go down 5 millivolts. It can go up to whatever like,


[User] Please transcribe this text

[Assistant] And if I plug this up all the way, so what happens if I-


[User] Please transcribe this text

[Assistant] Pull this voltage down. Worst case scenario, this transistor turns off.


[User] Please transcribe this text

[Assistant] If transistor is turned off, this current is the only current that can go through this resistor, pulled out of the resistor. And 100 microamps times 50 ohms is 5 millivolts. It's bad. It cannot swing low.


[User] Please transcribe this text

[Assistant] Well, we can crank up this current, but what should this current be for this to be able to swing 5 volts?


[User] Please transcribe this text

[Assistant] Yes. So we need to do something else. Exactly. That's right. Push pull, for example, right? We can use a push pull.


[User] Please transcribe this text

[Assistant] Because we need something that can dynamically provide current. You can't just like rely on static current because it's just excessive. It's not practical. I mean, it depends on what you're trying to do. I mean, maybe something like that. Yeah, no, I'm gonna throw, you know, a watt.


[User] Please transcribe this text

[Assistant] So I can go use 50 ohms, fine. But then if you have like 30 ohms, then you're gonna be short.


[User] Please transcribe this text

[Assistant] The good thing about dynamic output stages is that they can provide current as you need them. Not just


[User] Please transcribe this text

[Assistant] Just a fixed amount of, this is the maximum current I can give you at no more. So, you can try to use some sort of a push pull.


[User] Please transcribe this text

[Assistant] Relatively simple choice, but it's a logical choice. So we have a push pull like this.


[User] Please transcribe this text

[Assistant] And we know, so this is like that. And the most basic push pull was like that. So if I take this and plug it into here, for example, would this work?


[User] Please transcribe this text

[Assistant] Well, first of all, this push-pull we know that has dead zone, right? We talk about the output stages, this kind of thing, because you need to be at least a VDD, VCC, I'm sorry, VBE on above.


[User] Please transcribe this text

[Assistant] Something like that. And then you can try to keep them biased one way or another. You can actually provide them with some sort of a bias.


[User] Please transcribe this text

[Assistant] I'm gonna draw it this way for now, we'll deal with it later. We'll make changes. Let's say if I could do this.


[User] Please transcribe this text

[Assistant] So I have to provide some, so what this branch is doing is that you're running this current through this branch to make sure that whatever voltage you have here, you go a VBO down and a VBO up. So this voltage and that voltage can be substantially the same.


[User] Please transcribe this text

[Assistant] And you go a VBE up or a VBE down, so this can be. So this way you get rid of that crossover distortion. We've talked about this before when we talked about, uhm, output stages.


[User] Please transcribe this text

[Assistant] This is the RON, at 1 milliamp you're looking at 100 kiloohms, right?


[User] Please transcribe this text

[Assistant] And at 1 milliamp here you're looking at 50 kilo ohms. Your GM here at 1 milliamp is going to be 40.


[User] Please transcribe this text

[Assistant] And, okay, so what is the impedance that's presented here? What do you see looking into here? If you were looking into here. This is not the way it should be. I'm just showing the progression. But, we'll see. What's that impedance?


[User] Please transcribe this text

[Assistant] Well, let's talk about this. What is the impedance looking through here? Let's say you're swinging high. Let's say this is driving most of the current. Right?


[User] Please transcribe this text

[Assistant] So let's kind of look at the lower bound of that. Lower bound of that is just RL times beta. Right? So it's 50 ohm times beta, that's 5 kilo ohms. Right? And this is another RM in series with that.


[User] Please transcribe this text

[Assistant] Because it's diet-connected, right? It's just, you just see the alpha or, or, or, doesn't matter.


[User] Please transcribe this text

[Assistant] You see an RM, so this is not going to be significant. So looking, you're looking here around 5 kilo ohm. Ish. Right?


[User] Please transcribe this text

[Assistant] So this is clearly too low, because you're looking at 50 kiloohms and 100 kiloohms still is not enough. You need to have another stage of


[User] Please transcribe this text

[Assistant] That's fine. But the question is, how do you apply this input to that guy? You can, there are different ways of doing that, and again, this is not necessarily the way we are doing it right now, it's not necessarily the best way for other limitations, but it's okay. So, let's say you provide a buffering.


[User] Please transcribe this text

[Assistant] So now you get another factor of beta, so now you're looking at 500 kilo ohm. Looking into here. Right?


[User] Please transcribe this text

[Assistant] And that's okay, because you're looking at 50 kilo ohm, 100 kilo ohm, and 500 kilo ohm. Is this okay? Are we good now?


[User] Please transcribe this text

[Assistant] Okay, let's find out how high and how low the inputs, the output can go.


[User] Please transcribe this text

[Assistant] Yeah, okay, let's, let's see. Let's find out. That's a good question, right? So you're saying that what happens to the voltage ranges? Let's find out. So let's see. Okay.


[User] Please transcribe this text

[Assistant] So this, for this voltage to get to a Vsat, this voltage needs to get to a Vsat. Right? Can it get to a Vsat?


[User] Please transcribe this text

[Assistant] If you, if you pull this voltage down, this can go, SAT gets saturated, this can go to Vsat.


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[Assistant] So this would be a VSAT below VDD. So you can drop a VCC minus VSAT here. And if you add VCC minus VSAT here,


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[Assistant] This voltage would be VCC minus Vsat minus a VBE on. Then you go up a VBE and then you come down a VBE. Right?


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[Assistant] So you basically would be at the same level, so you would have Vcc minus Vsat minus Vbe.


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[Assistant] Again, similar situation here. If this goes to be sat above negative ECC, this is going to be a VBE below that, this is going to be a VBE above that, and then you can go there. How low can this go is determined by this guy.


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[Assistant] But if it's made out of a transistor, like that, it can go to Vsat. So it's gonna be negative Vcc plus Vsat. Right? Vsat above negative Vcc.


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[Assistant] The reason is that this node can go low, could get closer to this lower supply because it's only limited by Vsat here, but it can't go as high because there's a VBE plus a Vsat here.


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[Assistant] But let's, let's look around and see what we need to, because we have a whole bunch of these little things that we have to take care of. We need to create a reference branch to bias everything with. So let's do that. What kind of reference branch do we need to make?


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[Assistant] You saw that PTAT references are probably a good way of biasing these things. So let's make a proportional to absolute temperature. What you can do, you can basically take a PNP or NPN. You have both at your disposal here. You want to make two. There are many different ways to make this.


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[Assistant] You wanna make that one that has a larger IS.


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[Assistant] Or, you can make it with the floating mirrors or the op-amp style. Let's just make it with the floating mirrors. Or with a simplified one stage op-amp. You can, if we assume that we have that kind of a headroom to generate, use cascodes, you can use cascodes.


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[Assistant] You can do this, and then you can, so this is the isolator part of the floating mirror. This is the mirror.


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[Assistant] Part of it that forces the two currents to be equal. Put these things on the other side.


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[Assistant] And, so this is a PTAC. The current in this thing is going to be a VT reference, KT over Q reference, as we discussed before, right?


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[Assistant] So now you want to replicate this in places where you need. So you need, for example, a current source here, a current source there. So we'll make this into current sources.


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[Assistant] So you can take these two, go over here and come here.


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[Assistant] Now you need to scale them properly, so let's say you make this branch a, I don't know.


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[Assistant] And we decided, what was this? This is 1, 10, 100 microamps too? I don't know. Let's set it to 1x. If you need more current, you will make it a 2x or something like that, so you get...


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[Assistant] So that's the top part of it. You need to also produce a


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[Assistant] You copy this, generate the reference branch, so you copy it here, so it's gonna be a 1x, 1x, this is gonna be another 1x,


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[Assistant] Transistor is 10 times larger. And then you go, this is probably going to be another 10x.


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[Assistant] And this probably is going to be another 10x.


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[Assistant] And we forgot about this guy. So we'll continue here.


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[Assistant] We'll make this another 10x. So we have those. And then we're still missing a few things. We are, we need to generate this bias voltage.


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[Assistant] But now you remember, this is not going to swing a lot here. So you have room to play with.


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[Assistant] Maybe a couple VBEs above the ground, so what happened above this, so what I can do, I can make, so this is a VBE VBE, so maybe I can drop three VBEs. Here, I'll make a branch.


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[Assistant] And this is okay, because again, this is not going to swing a lot. Uhm.


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[Assistant] It would have probably been, actually you know what, this is not a very good idea. There's a problem with this.


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[Assistant] Let's change this, because you want this to be reference to the lower side. This is now reference to the upper side. This is reference to the higher supply.


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[Assistant] You want, I want this to be referenced to the lower supply to some extent so you can actually make that reference branch or diode connected branch here.


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[Assistant] This is really not connected here.


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[Assistant] And on the top, I want to have a current source feeding that.


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[Assistant] How can you do that? You can put a little resistor here and put another transistor that would steal the base current of this guy. And one here that would steal the base current of that guy. Let me show you what I mean by that. So for example, if I put a resistor here,


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[Assistant] So, there's a way, basically, you put a resistor here and you put a transistor here that draws the current and turns this one off if there's too much current flowing through it, but yea, that's not. Let's stick with the one we have, because


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[Assistant] What do these two transistors do? What's the role of these two transistors?


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[Assistant] So this is basically a differential pair at the input, right? So try to answer these questions that I'm asking you, even if you're not the person I'm asking. Okay, so what do these two transistors do? Think about it. What's their role?


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[Assistant] They provide CASCO, they provide an output impedance that's larger. What's the role of this group of four?


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[Assistant] It's a current mirror, right? This cascode part increases its output resistance and this is basically the mirror. Uhm, what do, what is the role of these guys? This branch. What is this doing?


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[Assistant] Increasing resistance. This is a buffer, right? Right? How about this branch? Somebody who hasn't answered yet.


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[Assistant] Also another buffer, right? This is another buffer. This is increasing the input resistance. Yes.


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[Assistant] You're trying to present a large load resistance. The next stage doesn't load the previous stage.


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[Assistant] So it basically multiplies, every one of them multiplies the load it sees, the output, by a factor of beta, and it presents it to the input. Roughly, right?


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[Assistant] These three essentially are buffers, right? What is the role of this transistor?


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[Assistant] It's a current source for this buffer, right? What does this transistor do? Somebody else, somebody who has an answer.


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[Assistant] Right? This is the gm of the second gain set. This is an important transistor. When all of them are important. This is particularly doing something important. Uh, what is the role of this guy? Go ahead.


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[Assistant] Current source is an active load for this guy, presenting a high result. What does this stage do?


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[Assistant] Another buffer, right, it's another follower, increases the input resistance. Why do we have these two transistors here? What do they do?


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[Assistant] Crossover distortion, they provide a VBE shift, so you have that shift when you try to drive the output, so you don't clip, right? What is the role of this guy?


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[Assistant] It's a current source, exactly. It's a current source for this branch. It biases this branch. What is this transistor doing?


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[Assistant] It's part of the push-pull. It's the follower for the output. It's the driver of the output. This has to be a pretty big transistor. So is this one. Uhm, what's happening here?


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[Assistant] Right, it's providing a V bias here through fixed current going through these guys maintaining this cascode base, constant base voltage. What is the role of this entire segment?


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[Assistant] It's a ptat, right? I mean it's a proportional to temperature part. This part is doing what?


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[Assistant] It's a, it's a floating part of the mirror, so it's basically just like this is the, this forces these two voltages to be equal. Right? What does this upper part do? It forces these two currents to be equal.


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[Assistant] And as a result, you basically subtract this from that, and then you drop the difference of two VBEs across the resistor, which would generate a VT. A thermal voltage. A PTAT. That's used to bias everything else. I think we covered everything, right? How many transistors are there?


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[Assistant] I'm gonna do it. Today's the day. I just knew it.


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[Assistant] Well, hello and welcome to this lesson where I'm going to talk about dream jobs.


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[Assistant] Dream jobs are the types of jobs that many people think they want or many people do want. There might be a slight difference. A dream job is a job that very few people maybe do, but a lot of people think they would like to do it. You can see on my title slide, I have a picture of Matt Damon.


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[Assistant] He is an actor and being an actor is one type of dream job I'm sure there are many people in the world that dream of being a famous actor


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[Assistant] They dream of being in movies or on a television show, but certainly being an actor is a type of dream job. So I hope you enjoy this English lesson where we're going to talk about dream jobs.


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[Assistant] Probably most popular dream jobs in the world is the job of being a professional athlete.


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[Assistant] I think many kids, when they are growing up, they will play a certain sport and their dream will be that someday they will get paid to play that sport. Someday they will be a professional athlete. That might be a basketball player, a football player, American football, or a football player, what we call soccer.


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[Assistant] Uhm, it could be anything. In Canada, many kids dream of becoming hockey players. So professional athlete is definitely, probably the number one dream job on the list. By the way, this list isn't in any particular order.


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[Assistant] But I started with this. This is actually Fred Van Vliet. He plays for the Toronto Raptors, which is, uhm, a team in the National Basketball Association. So,


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[Assistant] Definitely a great place to play. I think there are many young Canadians who are dreaming of playing basketball now as a dream job. Where do professional athletes work?


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[Assistant] They work in stadiums. They work in arenas. They might play on the football field or the pitch. Uhm, and definitely, I'm trying to think if there's any other words. When I go see a hockey game, it's at a hockey arena. Uh, when you go see a football game, it's at a stadium. So those are the places that a professional athlete would work.


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[Assistant] Uhm, I added this one next just for a little bit of humor, uh, and it's circus performer. In English, and I'm sure in other languages as well, sometimes people dream of running away to join the circus.


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[Assistant] It's a phrase you use when you're not happy with where you're at in life, and you might say, you know what, I might just run away and join the circus.


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[Assistant] Uhm, some people do actually join the circus though. Canada has produced a circus troupe called Cirque du Soleil, which is a very popular group that does all kinds of circus acts. Anyways, where would a circus performer work? They would work in the big top.


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[Assistant] When you go to a circus a long time ago, there used to be big tents.


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[Assistant] Cirque du Soleil performs inside, of course, but it used to be that you would go to a tent and you would see the circus performers in the big top. So when you read a book or when you watch a movie like The Greatest Showman, which is about circuses, uh, you will see large tents and elephants and jugglers


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[Assistant] Another dream job would be that you learn how to do card tricks or illusions. Maybe you want to learn how to, uh, make it look like you're sawing someone in half when you're really not. Maybe you would like to be a magician. Uhm, I know a couple of my kids have learned some magic tricks. They've learned some card tricks in the past.


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[Assistant] And it's really fun, uh, to watch them do it. But maybe your dream in life, your dream job is to become a magician and to have your own show in Las Vegas.


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[Assistant] Maybe you want to be a rockstar. So definitely a dream job for many people. This is probably on the same level as professional athlete. I think many kids in the world dream of being a professional athlete.


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[Assistant] Or they might dream of being a rock star. This is Bono from U2. Uhm, he's an amazing, well-known rock star.


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[Assistant] Great singer, uh, and uh, I've never been able to see them in concert. I should sometime go and see them because they're getting a little bit old.


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[Assistant] But anyways, rockstar, definitely. Where do rockstars perform? They perform on a stage. If you were a rockstar, you might go to a music studio to record an album or to record a song. You would maybe play to a sold out show in a stadium.


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[Assistant] Often, rock stars and rock bands will rent out large stadiums where you would normally see a sporting event so that they can do a live concert.


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[Assistant] Picking up garbage, but Joe's just really good at it. He's a rock star. Uhm, we have another term, singer-songwriter.


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[Assistant] Uhm, a singer-songwriter is someone who sings the songs that they've written. Uhm, someone like Taylor Swift, I believe, is a singer-songwriter. Uhm, Alicia Keys is a singer-songwriter. Uhm, these are people who spend their time writing music and then performing their music as well.


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[Assistant] So when they're doing the songwriting part, they're probably at home or somewhere quiet where they can just think clearly and be creative.


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[Assistant] And when they're done writing the song, they would go to the studio to record the song.


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[Assistant] Lolly in the chat says woohoo, so I'm a rockstar, yes. Uhm, and you also just have the dream job of being a musician. Many people when they are young learn to play the guitar or the piano or the violin. They learn an instrument and they might have a dream to become a professional musician.


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[Assistant] Maybe not a rock star, maybe not a singer songwriter, but still find a way where they can be paid.


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[Assistant] So often when you go to a studio, there are musicians who can work. They're called session musicians. Maybe you want to play in an orchestra. Maybe you are really good at playing the cello or the violin or the timpani. I hope that's actually a kind of drum.


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[Assistant] Looking to learn an instrument and your dream job is to be paid to play that instrument. And it might be as simple as playing on the street.


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[Assistant] We have something called busking. When you busk it means you play an instrument on the sidewalk and people put money into maybe your guitar case and we would call you a busker. Or maybe you want to be a music producer. A music producer is someone who


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[Assistant] It helps a musician or a singer-songwriter or a rock star or a rock band record their music in the studio. They might do the sound engineering, they might actually provide some of the money to get it done, but music producers are another way to work in the music industry, if that's your dream.


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[Assistant] Uhm, and if you're not a good musician or singer, but you're good at the technical side of things, or you're good at the money side of things.


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[Assistant] And then maybe your dream job is to become an actor. Maybe your dream is to be in Hollywood movies or Bollywood movies or movies in your own country. Uhm, actors definitely are very cool. A couple things I wanted to mention when we got to this slide. We use the word actor to refer to both men and women.


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[Assistant] We use the term actress when we give out awards, but we don't generally use the word actress anymore in news articles or when we're talking about female actors. We usually just say actor. Okay, so you would say he's an actor or she's an actor.


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[Assistant] But you would say, oh, she won best actress in her recent movie. So the term actress is used in formal things like giving awards, but generally we just use the word actor now.


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[Assistant] Uh, and then maybe your dream is to be a YouTuber. This is Felix Schellberg, also known as PewDiePie, probably one of the most famous YouTubers in the world. Uhm, a YouTuber is someone who buys a camera,


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[Assistant] Generally, YouTubers, when they first start out, they make all of their videos at home. They edit them on a computer or maybe even on their phone. They might use their phone as their camera and they might edit on their phone and they upload their videos to YouTube.


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[Assistant] Uh, less of a dream job is to be a podcaster, but a podcaster is similar to a YouTuber, but instead of recording video, they simply record audio. So maybe your dream is to become a podcaster, to have a podcast.


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[Assistant] Generally, podcasters will have a small studio in their house with a microphone, uhm, and then they will record their own voice or they will have other people who come as well and they'll record a conversation.


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[Assistant] But maybe your dream job is to become a podcaster. Maybe that's your goal in life is to become a podcaster, uh, and just use your, maybe you have a smooth buttery voice, a really nice sounding voice, and your dream is to just talk and get paid for it. That'd be pretty cool, wouldn't it?


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[Assistant] An influencer is someone who has a large following on YouTube or Instagram or just in the uh, the news. Someone who is extremely famous.


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[Assistant] And because they have so many followers, they can influence what people decide to buy or do. A great example, I think this is Kim Kardashian. I'm not super familiar with the influencers of the world, but if Kim Kardashian said that Portugal is the best place to go on vacation,


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[Assistant] A whole bunch of people in the world would decide to go to Portugal for their vacation.


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[Assistant] If Kim Kardashian said that she loves spending the winter in Paris, France.


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[Assistant] More people would become interested in going to Paris Brands. If she wears a dress from a certain company, more people will buy that dress. So an influencer is someone


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[Assistant] Who has many many followers on a social media platform and maybe in the tabloids. Tabloids are newspapers that follow the lives of celebrities.


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[Assistant] Or maybe they're just famous because they're on television or in movies. They are called influencers.


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[Assistant] I'm not an influencer. I'm just a guy who teaches English on YouTube.


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[Assistant] Uh, so Vito before the lesson was asking about, uh, Vito said that, uhm, their dream job was to just have so much money they didn't need to work. So there is a word for this or a term and it's independently wealthy. I once went to school


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[Assistant] Sorry, I once was in a university class and there was an older gentleman there. He was about 35 years old. At the time I was about 20. And I asked him, what do you do for a living? And he said, oh, I'm independently wealthy.


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[Assistant] So if you are independently wealthy, you have so much money that you don't need to work. You have so much money that the interest you earn on your investments is enough for you to live off of. Hopefully you understood that. I am not independently wealthy.


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[Assistant] I'm not even dependently wealthy. That's not a term, by the way. Uhm, I am not independently wealthy. I need to go to work every single day.


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[Assistant] I need to earn my keep. I need to have a paycheck so that I can pay my mortgage, feed my children, and pay my bills. Uhm, someday, maybe when I'm 65 and I'm retired,


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[Assistant] I will have a pension and I will be able to live without working. But at this point in time, this is not me. At all.


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[Assistant] Uhm, another dream job, and this is a common dream job, this is commonly mentioned by young children. If you ask young children, uh, what do you want to be when you grow up?


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[Assistant] Sorry, I should have taught that phrase earlier. When you ask a child what job they want to do when they're older, we usually say, what do you want to be when you grow up?


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[Assistant] And they might say that they want to be an astronaut. An astronaut is someone who works either at NASA or the European Space uh,


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[Assistant] So agency, uh, or maybe who else has space programs? I know China has a space program. I know other countries support other countries space programs.


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[Assistant] Where does an astronaut work? Well they work at the place where they launch rockets. By the way, in English, when a rocket gets launched at the end,


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[Assistant] Right before it launches, we say five, four, three, two, one, and then I always yell blast off. It's pretty common, I think, for people to do that. So astronauts work at a, uhm,


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[Assistant] Let me see here, uhm, like a space center on earth. And then they might also work at, uh, in a space station. They might go up in a rocket to work on the space station. And right now I think


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[Assistant] The world is working towards having a base on the moon and maybe a base on Mars. So someday if you become an astronaut, you might be able to work somewhere like that.


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[Assistant] Maybe your goal is to become a chef. Maybe your goal is to be uhm, a famous restaurant owner. Maybe you want to be someone who creates new kinds of food dishes. You're going to mix together different


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[Assistant] A celebrity chef is someone who has a TV show or what we call cooking shows, uh, on television. So if you watch someone like Gordon Ramsay, he is a celebrity chef.


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[Assistant] A chef works usually at a restaurant and the chef works in the kitchen of that restaurant. Although sometimes, uh, chefs become a personal chef. So they actually work at someone's house. That would be someone who is independently wealthy might hire a personal chef. That's a possibility.


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[Assistant] Maybe your dream is to become an artist. Maybe you would like to be a painter. Maybe your dream is to use your artistic talent to express yourself in different forms. Maybe you like to do pottery. Maybe you like to do sculpting. Maybe you like to


[User] Please transcribe this text

[Assistant] It's very difficult, I think, to become a highly paid artist. There's another term in English called starving artist. When you're starving, it means you don't have enough food. Many artists, when they are first starting out,


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[Assistant] Not a lot of people buy their works of art. Uh, so they're in their studios, they're creating works of art and they're having art shows, uhm, and at an art gallery and then they hope people buy their paintings or other art and maybe it doesn't happen. So I used a bunch of terms in there. Art show, maybe they're having an opening. An opening means that you're having


[User] Please transcribe this text

[Assistant] All of your art displayed at an art gallery, hoping that someone will buy it.


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[Assistant] I'm not an artist. I can draw stick people. I think you know what stick people are. It's when you draw people just using lines. That's the extent, uh, of my ability to draw.


[User] Please transcribe this text

[Assistant] Maybe your dream is to become a writer. Maybe your dream job is to write a book. Maybe you want to become a journalist and write newspaper articles for the newspaper. Maybe your dream is to become an author.


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[Assistant] So, little bit of a difference between writer and author. Writer is a general term. So I could say, uhm, oh I'm a writer for this magazine, or I'm a writer, I write children's books.


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[Assistant] An author is a writer who specifically writes books. But maybe your dream is to put pen to paper and to write some beautiful, beautiful books.


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[Assistant] Maybe you want to be a model. This was never my dream. Maybe you're, unless if there was a company that only made blue plaid shirts.


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[Assistant] For middle-aged men who are almost 50 and they were looking for a model to show the shirts to the public.


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[Assistant] Then I would become a model, but maybe you are very attractive. Maybe you are an attractive man or woman and people keep saying you have a beautiful face. You have really nice bone structure like your cheekbones are really high. You have beautiful eyes.


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[Assistant] But you should become a model. A model would work at a fashion show. A model would go to a photo shoot to have their picture taken. And basically their job is to look amazing while showing off clothing, jewelry, and other items that fashion designers are creating.


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[Assistant] Maybe your goal is to become a fashion designer. Your dream job is to design clothing.


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[Assistant] Maybe you love sewing things together. You love the feel and look of fabric and you like to put different things


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[Assistant] Different outfits together and people are always saying you just look amazing. And then if you say, yeah, well, I made this myself. Maybe your job, your dream job might be to be a fashion designer.


[User] Please transcribe this text

[Assistant] Uhm, a fashion designer would work in their workshop, uhm, or they might call it a studio. We sometimes use the French word atelier as well to talk about a place.


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[Assistant] Maybe you want to work in a hospital and help deliver babies and give people needles. Maybe your dream job is taking care of people.


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[Assistant] I have enormous respect for nurses in the world. They do an amazing job. If any of you work in healthcare as a nurse or doctor, I just wanna thank you right now. You are just awesome people. Thank you. Especially during this last


[User] Please transcribe this text

[Assistant] Maybe you want to, uh, just be what we call a general practitioner or family doctor and you just wanna be able to, uh, find out what's wrong with people, have them describe their symptoms, and then diagnose what's wrong and give them a prescription or some form of treatment.


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[Assistant] Again, both nurses and doctors work either at hospitals or medical centers. Uhm, there's a lot of different names for that. We have uhm,


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[Assistant] Urgent care centers, et cetera, but generally nurses and doctors work in a hospital.


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[Assistant] Maybe you want to be a lawyer. Maybe you want to defend people in a court of law. Maybe you want to be able to take part in lawsuits. Maybe you want to be able to advise people about what to do with all their money if they're independently wealthy when they pass away or when they die.


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[Assistant] So you would then go to law school and your primary place of work would be your law office.


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[Assistant] Or in the courts, okay? So you might be in a courtroom.


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[Assistant] Or you might be in your law office. If you become a lawyer, you will probably become wealthy as well. No guarantee, but I know this. We have many students who come from other countries to study in Canada. Many of them want to become a doctor or a lawyer. Those are the two biggest goals that I have noticed.


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[Assistant] Maybe you want to become a photographer. Maybe you love taking pictures. You're really good at taking pictures. Maybe you want to work for the magazine called National Geographic.


[User] Please transcribe this text

[Assistant] So maybe you want to travel, maybe you want to use your photography skills to take beautiful photos so that people can see them when they read magazines or maybe you even put them online. Uhm, but maybe you, your dream job is to become a photographer. Uh, where does a photographer work? Everywhere.


[User] Please transcribe this text

[Assistant] Photographers go where the action is. Photographers go where they know they can take beautiful photos. Uhm, and then they'll probably have a really nice camera and a tripod to put it on so they can take those photos.


[User] Please transcribe this text

[Assistant] Maybe your goal is to become a pilot. I kinda mentioned this earlier. A pilot is someone who flies a plane or a helicopter.


[User] Please transcribe this text

[Assistant] Maybe you want to join the Air Force in your country and become a jet fighter pilot or maybe you want to fly helicopters, uh, in the Air Force and then after you're done serving in the military, you might want to work for a commercial airline and fly for Air France or Air Canada or something like that.


[User] Please transcribe this text

[Assistant] But maybe your dream job is to be a pilot. Where does a pilot work? A pilot sits on the flight deck or in the cockpit and flies the airplane or flies the helicopter. Maybe you wanna be a CEO. A CEO is a chief executive officer. This is someone who is in charge of an entire company.


[User] Please transcribe this text

[Assistant] So maybe you want to be the CEO of Facebook or you want to be the CEO of the Ford Motor Company. Maybe you want to be the CEO of BMW. This would mean that you are the boss. You are the boss of all the bosses. You are at the top.


[User] Please transcribe this text

[Assistant] Uhm, I have no desire to have that much authority or power.


[User] Please transcribe this text

[Assistant] Uhm, with, uhm, jobs like this, I think there's also a lot of stress because you have to make sure that the company makes money. But maybe you want to be a CEO. A CEO works in the boardroom.


[User] Please transcribe this text

[Assistant] Or in their office. So your, their office is where they have a desk and a phone. The boardroom is where they meet with other people.


[User] Please transcribe this text

[Assistant] Maybe you want to be an entrepreneur. Maybe you want to think of things or invent things or maybe you just want to start your own business. So we use the French word entrepreneur. An entrepreneur is someone who thinks, I could buy


[User] Please transcribe this text

[Assistant] Maybe you want to be a business owner. This picture made me laugh because I feel like this lady is a business owner and she's in her office and she's looking out wondering where everyone is.


[User] Please transcribe this text

[Assistant] Because it's probably a holiday. So when you own a business,


[User] Please transcribe this text

[Assistant] You probably, uh, don't work, uh, sorry, when you are a business owner, you probably work on holidays. So I felt like she was looking to see where all of her workers were and then remembering that it's actually a holiday. But a business owner


[User] Please transcribe this text

[Assistant] Would be someone who runs a business. A little different than an entrepreneur. A business owner.


[User] Please transcribe this text

[Assistant] An entrepreneur is a business owner, but a business owner is not necessarily an entrepreneur. Remember, an entrepreneur starts a business. A business owner might simply buy an existing business from someone and run that business.


[User] Please transcribe this text

[Assistant] Maybe you're self-employed. We had this mentioned in the chat earlier. When you are self-employed, you work for yourself. So Jen, for instance, is self-employed. She has a flower farm. She grows and sells bouquets of flowers. She is self-employed. A self-employed person would work


[User] Please transcribe this text

[Assistant] Or a lawyer, or uhm, a flower farmer, their place of work would be slightly different.


[User] Please transcribe this text

[Assistant] But if you want to become a computer programmer and you want to create video games, we would call you a video game designer.


[User] Please transcribe this text

[Assistant] Uh, you would work in an office with other people. You would primarily sit at your desk, at your computer, writing computer code and making video games. So maybe your dream job is to be a video game designer. Who knows? I like writing computer programs.


[User] Please transcribe this text

[Assistant] But it's never been my goal in life to be a video game designer. It's more of a hobby.


[User] Please transcribe this text

[Assistant] Uhm, then something I would want to do for work.


[User] Please transcribe this text

[Assistant] Uhm, oh, I do have a video game tester. Yes, many of my students dream of becoming video game testers. And again, this job does exist. It's probably not as fun as you think. I don't think it would be fun to play a game for eight hours a day every day, but I guess you're getting paid for it. Who knows?


[User] Please transcribe this text

[Assistant] Maybe you have a beautiful voice and you tried podcasting and it didn't work out, but you have a beautiful voice or maybe you can make different voices. Maybe you're really good at voice acting.


[User] Please transcribe this text

[Assistant] You might want to become a voice actor or a voice over artist. So a voice over artist comes in and they read a script into a microphone. They would go to a studio and they would have their voice recorded for television commercials, for radio commercials,


[User] Please transcribe this text

[Assistant] Maybe you can do, like, I can't do funny voices, but maybe you can do all different funny voices, and your dream job is to be a voice over artist.


[User] Please transcribe this text

[Assistant] Or a voice actor. So two terms there. I forgot to put the one on the slide.


[User] Please transcribe this text

[Assistant] Maybe you want to be a race car driver, a very dangerous job, but maybe you want to drive in F1, Formula 1. Maybe you want to drive in at your local racetrack, you want to drive a race car, uhm, and maybe you want to drive laps around the track really fast and pull into the pits and have your tires changed by your pit


[User] Please transcribe this text

[Assistant] Maybe driving a race car is the future. This is not Formula One, by the way. In North America, we also have NASCAR as well, a very popular type of racing. And then I think there's IndyCar. I watched NASCAR, but I haven't watched IndyCar or Formula One very much. Maybe you want to be a mascot.


[User] Please transcribe this text

[Assistant] A mascot is someone who dresses up for a sports team and helps entertain the crowd at a stadium or arena. This is Ace from the team the Toronto Blue Jays. So they are a baseball team in Toronto. Remember I said we share


[User] Please transcribe this text

[Assistant] Uhm, we have teams that play in leagues in North America. Baseball is one of those leagues. So the Toronto Blue Jays play against all of the American teams, which is kinda cool.