Question

Choose the incorrect statement for JFET(s).

(a) Maximum transconductance occurs at VGS=0

(b) Transconductance decreases linearly with VGS

(c) Transconductance increases linearly with IDS

(d) Transconductance does not depend on VDS

The question was posed to me in an interview for internship.

I would like to ask this question from JFET Amplifier topic in chapter FET Amplifiers of Analog Circuits

Answer 1

The correct choice is (c) Transconductance increases linearly with IDS

The best explanation: Maximum transconductance occurs at VGS = 0, and it lies between 0-gmo. Transconductance decreases linearly with VGS according to equation gm = gmo(1-VGS/VP). However, gm ∝ \(\sqrt{I_{DS}}\), which is a parabolic increase, not linear.