user11995: I'm thinking about making my own "arduino" low power board but I have a question about the atmega328. Is the output voltage on the pins always 5v or it depends on the input voltage I gave to the atmega?
Thanks in advance.

user4143: It depends on the input voltage you give it.  If you run the ATMega328p at 3.3V then you get 3.3V out.  If you run it at 5V you get 5V out.
A word of caution about running at lower voltages:  The chip can't run as fast when it has a lower supply voltage - that's why you will see the 3.3V Arduino boards running at 8MHz (or 12MHz at a pinch).

11995: <p>I'm thinking about making my own "arduino" low power board but I have a question about the atmega328. Is the output voltage on the pins always 5v or it depends on the input voltage I gave to the atmega?</p>

<p>Thanks in advance.</p>
 4143: <p>It depends on the input voltage you give it.  If you run the ATMega328p at 3.3V then you get 3.3V out.  If you run it at 5V you get 5V out.</p>

<p>A word of caution about running at lower voltages:  The chip can't run as fast when it has a lower supply voltage - that's why you will see the 3.3V Arduino boards running at 8MHz (or 12MHz at a pinch).</p>
