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A common-emitter amplifier has a voltage gain of G. If the transistor in it has transconductance 0.03 mho and current gain 25, and it is replaced by another transistor with transconductance 0.02 mho and current gain 20, what will be the new current gain?
- 1.5 G
- 1/3 G
- 5/4 G
- 2/3 G
Correct answer: 2/3 G
Solution
For a common-emitter amplifier the gain is proportional to the transconductance (gain = gm * R_load). Replacing gm = 0.03 by 0.02 scales the gain by 0.02/0.03 = 2/3, giving (2/3)G.
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