user57675: I am trying to use a DC power supply. I am thinking whether I can use this power supply to provide power for Sim800L module. After some research, I gathered that the Sim800L module requires a max current of 2A during GPRS transmission at 3.8-4.2 V (4.0 recommended). With the power supply I can easily configure the voltage at 4.0V. My question is: for this setup, do I need a DC-DC Buck Converter as in this one for regulation/step-down (not sure which)? 

user2967: The lab power supply you linked is serious overkill for your needs. It shouldn't need a separate voltage regulator or buck converter, since I assume that it provdes a voltage and current regulated supply.
A regulated, fixed voltage 4V power supply that can provide 2A is what you want. That will probably cost < 1/10 of the amount of the lab supply you linked. The challenge is to find a 4V supply. (Most regulated power supplies are either 3.3V or 5V, since those are common voltages for solid state electronics.)
That said, the linear voltage regulators are usually adjustable with a decent voltage range using a resistor.
You could always build your own voltage regulator using a linear voltage regulator rated for 2A, plus a resistor and a couple of capacitors. You could either feed it from an unregulated 6V power supply or use a transformer, bridge rectifier, and capacitor to provide an unregulated DC input to a voltage regulator.
Edit:
With a little googling I found a few 4V 2A power supplies online. This one, for example:
https://www.alibaba.com/product-detail/US-AC110-220V-To-DC-4V_62155516966.html?spm=a2700.7724857.normalList.14.a5e64009aUU1ln&s=p
(That link is to a wholesale manufacturer that sells them in volume, but you may be able to find the same supply for single unit sale. A 2A switching 4V supply would meet your needs as well)

57675: <p>I am trying to use a DC <a href="https://mcs.com.bd/product/dazheng-ps-305d-dc-power-supply-3-digit-0v-30v-0a-5a/" rel="nofollow noreferrer">power supply</a>. I am thinking whether I can use this power supply to provide power for <a href="https://nettigo.eu/products/sim800l-gsm-grps-module" rel="nofollow noreferrer">Sim800L</a> module. After some research, I gathered that the Sim800L module requires a max current of 2A during GPRS transmission at 3.8-4.2 V (4.0 recommended). With the power supply I can easily configure the voltage at 4.0V. My question is: for this setup, do I need a <a href="https://www.addicore.com/lm2596-module-p/ad281.htm" rel="nofollow noreferrer">DC-DC</a> Buck Converter as in this one for regulation/step-down (not sure which)? </p>
 2967: <p>The lab power supply you linked is serious overkill for your needs. It shouldn't need a separate voltage regulator or buck converter, since I assume that it provdes a voltage and current regulated supply.</p>
<p>A regulated, fixed voltage 4V power supply that can provide 2A is what you want. That will probably cost &lt; 1/10 of the amount of the lab supply you linked. The challenge is to find a 4V supply. (Most regulated power supplies are either 3.3V or 5V, since those are common voltages for solid state electronics.)</p>
<p>That said, the linear voltage regulators are usually adjustable with a decent voltage range using a resistor.</p>
<p>You could always build your own voltage regulator using a linear voltage regulator rated for 2A, plus a resistor and a couple of capacitors. You could either feed it from an unregulated 6V power supply or use a transformer, bridge rectifier, and capacitor to provide an unregulated DC input to a voltage regulator.</p>
<h2>Edit:</h2>
<p>With a little googling I found a few 4V 2A power supplies online. This one, for example:</p>
<p><a href="https://www.alibaba.com/product-detail/US-AC110-220V-To-DC-4V_62155516966.html?spm=a2700.7724857.normalList.14.a5e64009aUU1ln&amp;s=p" rel="nofollow noreferrer">https://www.alibaba.com/product-detail/US-AC110-220V-To-DC-4V_62155516966.html?spm=a2700.7724857.normalList.14.a5e64009aUU1ln&amp;s=p</a></p>
<p>(That link is to a wholesale manufacturer that sells them in volume, but you may be able to find the same supply for single unit sale. A 2A switching 4V supply would meet your needs as well)</p>
