1.

If g is the transconductance and r is the resistance due to channel length modulation – what is the total voltage gain if both M1 and M3 has channel length modulation?(a) R / ((1/g || r) + R) * g * R * R / ((1/gm || r))(b) R / ((1/g + 4R) * g * R / ((1/g || r) + 3R)(c) R / ((1/g || r)) * g *R * R / ((1/g || r) + 2R)(d) R / ((1/g) * R * R * g * 4gThis question was posed to me at a job interview.I'm obligated to ask this question of MOSFET Amplifier with CD Configuration topic in chapter FET Amplifiers of Analog Circuits

Answer»

Correct option is (a) R / ((1/g || r) + R) * g * R * R / ((1/gm || r))

The BEST I can explain: This is a cascade of a FOLLOWER stage follower by a CS stage which precedes another follower stage. The gain due to each stage gets multiplied until we REACH the OUTPUT. For the first stage, the gain is R/ ((1/g || r) + R). The second stage has a gain of g * R while the final stage has a gain of R/ ((1/g || r) + R). The presence of r is due to channel length modulation. After multiplying the gains, we GET R/ ((1/g || r) + R) * g * R * R / ((1/gm || r)).


Discussion

No Comment Found

Related InterviewSolutions