Question

Voltage gain of common drain amplifier is always slightly less than _____

(a) 0.5

(b) 1

(c) 1.5

(d) 2

I got this question during an online exam.

The origin of the question is A Generalized FET Amplifier in portion Field-Effect Transistors of Electronic Devices & Circuits

Answer 1

Right choice is (b) 1

For explanation I would say: In common drain amplifier

Writing KCL at the source node ;

Gm(vin – vout) – gmbs vout – gds vout = 0

 vout vin = Gm / Gm + Gmbs + gds

Therefore gain is less than one.