AC Simulation Results

Stability

The following image illustrates the gain and phase plot of the system. The phase margin is found to be ≈ 62°. The criterion for stability is: the rate-of-closure at fcl = (Aol slope – 1/β slope) is 20dB/decade. The following gain plot shows both Voa (Aol) and 1/β. Without capacitor C1, 1/β experiences a zero and provides a rate-of-closure of 40dB/decade. Adding capacitor C1 creates a pole in 1/β and ensures the rate-of-closure is at 20dB/decade and therefore the circuit is stabilized. For more details, see TI Precision Labs - Op Amps: Stability - Introduction.