Second Order Control System Saved

This circuit is a second order control system that also functions as an error amplifier. The system has a pole at the origin for the purpose of tracking constant references with zero steady-state error. A zero, and another pole are also part of the transfer function. The purpose is to provide phase lead with the zero before the desired crossover frequency, and phase lag above the desired crossover frequency. Actually the crossover frequency of a greater loop, should be the geometric mean between the zero and pole frequencies.