The OP37 is a decompensated amplifier

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 Stability and compensation

Problem

The OP37 is a decompensated amplifier, specified stable only for closed-loop gains of 55 or more. An inverting amplifier is built with R1=10 kΩR_1 = 10\,\text{k}\Omega from the source to the inverting input and R2=40 kΩR_2 = 40\,\text{k}\Omega from the inverting input to the output. Someone argues: "The closed-loop signal gain here is −R2/R1=−4-R_2/R_1 = -4, whose magnitude, 44, is below the datasheet minimum of 55, so this circuit will be unstable." ((a)) Find the error in the reasoning. ((b)) Decide whether the circuit is actually stable, by computing the quantity the datasheet specification actually refers to.

Browse the problem library