A bipolar long-tailed pair is biased with a tail current

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Semiconductor devices and analogue circuits · Semiconductor devices and analogue circuits

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Problem

A bipolar long-tailed pair is biased with a tail current Itail=2 mAI_{\rm tail} = 2\,\mathrm{mA}, collector resistors RC=5 kΩR_C = 5\,\mathrm{k}\Omega on each side, and βF=150\beta_F = 150. Take VT=25.9 mVV_T = 25.9\,\mathrm{mV}. A resistor RER_E is now added in series with each emitter (equal on both sides) and its value is varied. ((a)) With RE=0R_E = 0, find the per-side transconductance gmg_m, the differential-output gain AdA_d and the differential input resistance RidR_{id}. ((b)) Repeat for RE=150 ΩR_E = 150\,\Omega. ((c)) Repeat for RE=400 ΩR_E = 400\,\Omega.

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