InterviewSolution
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InterviewSolution
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For a high frequency response of a simple C.E. stage with a transconductance of gm, what is Cout?(a) Ccs – Cµ*(2 + 1/gm*R2)(b) Ccs + Cµ*(1 + 2/gm*R2)(c) Ccs – Cµ*(1 + 1/gm*R2)(d) Ccs + Cµ*(1 + 1/gm*R2)This question was posed to me during an internship interview.The above asked question is from Effect of Various Capacitors on Frequency Response in division Transistor Frequency Response of Analog Circuits |
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Answer» RIGHT choice is (d) Ccs + Cµ*(1 + 1/gm*R2) Easy explanation: We have a capacitor from the collector to substrate, Ccs, which comes in parallel to the miller approximation of the capacitance from base to collector. The miller approximation DEFINES the latter as Cµ*(1 + 1/gm*R2). Since CAPACITORS gets added, when in parallel, the correct option is Ccs + Cµ*(1+ 1/gm*R2). |
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