Question

If gm=0.5mS, RS=2KΩ, determine ZO  for source follower?

(a) 2KΩ

(b) 1KΩ

(c) 3KΩ

(d) 1.5KΩ

This question was addressed to me during an interview.

Question is from The Common Drain Amplifier in section Field-Effect Transistors of Electronic Devices & Circuits

Answer 1

Correct answer is (b) 1KΩ

To explain I would say: ZO=RS||1/gm

=>1/gm=1/0.5mS=>2KΩ

2KΩ||2KΩ=1KΩ,

=>ZO=1KΩ.