1. The problem statement, all variables and given/known data Hi, I have a basic MOS common-drain amplifier as described below: - Drain connected to 5 V DC - Gate connected to an AC source on top of a 3 V DC source - Source connected to a 200 uA current source with a resistor R connected in parallel. The parallel connection goes to ground, and the output voltage (Vo) is taken across resistor R. If R approaches infinity, I heard someone explain that Vo > 3 - Vt - (Vgs - Vt) where Vt = thermal voltage. 2. Relevant equations 3. The attempt at a solution I'm not understanding how to get to this expression, because I had simply thought: Vo = 3 - Vgs, since it's just the voltage applied at the gate minus gate-to-source voltage. I'm not sure where the Vt comes from in the expression above. Thanks for clearing this up for me!