A modest-gain preamplifier IC has open-loop DC gain

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

Inside the Instrument, Ch Loop gain in real feedback circuits

Problem

A modest-gain preamplifier IC has open-loop DC gain A0=1000A_0 = 1000, input resistance Rid=50 kΩR_{\rm id} = 50\,\mathrm{k}\Omega, output resistance Ro=500 ΩR_o = 500\,\Omega, and one dominant open-loop pole at fp=100 Hzf_p = 100\,\mathrm{Hz}. It is wired as an inverting amplifier with R1=1 kΩR_1 = 1\,\mathrm{k}\Omega, R2=2 kΩR_2 = 2\,\mathrm{k}\Omega, driving a load RL=2 kΩR_L = 2\,\mathrm{k}\Omega. ((a)) Find the return ratio TT of the controlled source. ((b)) Find the direct transmission dd and the exact closed-loop gain ACLA_{\rm CL}, and state by how many per cent this differs from the ideal gain A∞=−R2/R1A_\infty = -R_2/R_1. ((c)) Find the frequency of the closed-loop pole.

Browse the problem library