Stability of AGC circuits containing peak detectors

Stability is examined for second-order automatic gain control (AGC) systems used to control the peak of narrow-pulsewidth signals. Stability limits for a system using a diode-type detector are determined by finding the system response when the detector is charging, finding the time at which it changes states, and then using the loop condition at this time as the initial condition when the detector is discharging. Stability is determined by comparing the initial and final values of the error for one cycle and using the ratio of these values as the loop gain in a discrete time model