An emitter follower biased at drives an emitter resistor directly from a…

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Semiconductor devices and analogue circuits · Feedback, operational amplifiers and analogue signal processing

Inside the Instrument, Ch Loop gain in real feedback circuits

Problem

An emitter follower biased at

I_C = 2\,\mathrm{mA}

drives an emitter resistor

R_E = 470\,\Omega

directly from a zero-resistance signal source (

R_s = 0

). The transistor has

\beta_F = 150

. Work at

300\,\mathrm{K}

, where

V_T = 25.9\,\mathrm{mV}

. ((a)) Find

g_m

and

r_\pi

, and hence the return ratio

T

of the controlled source

g_mv_\pi

. ((b)) Find the direct transmission

d

and, using the asymptotic-gain formula with

A_\infty = 1

, find the closed-loop (voltage) gain of the follower.

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