Question

If maximum power is transferred to the load R1, the transconductance is .02 and channel length modulation is neglected, what should be the value of the load?

(a) 50 Ω

(b) 32 Ω

(c) 16 Ω

(d) 10 Ω

I got this question during an online interview.

This is a very interesting question from MOSFET Amplifier with CD Configuration topic in section FET Amplifiers of Analog Circuits

Answer 1

Right option is (a) 50 Ω

For explanation I would say: Since the transconductance is .02, it’s inverse is 50. From the general expression of voltage gain of a source follower, we conclude that the load should be 50 Ω since the inverse of the transconductance is the impedance looking into the source of the MOSFET. For maximum power transfer, we have to match both the impedance.