Effects of nonlinear feedback in the frequency domain

A simple methodology to evaluate harmonic distortion in the frequency domain for circuits and systems made up of a nonlinear high-gain path with a nonlinear feedback network is presented. The approach provides compact closed-form expressions which constitute a direct extension of the classic ones valid at dc. The result improve our understanding of nonlinear frequency behavior in general feedback circuits and can even be used in manual design. The accuracy of the equations obtained was evaluated by comparison with computer simulations and measurements on an example circuit. Simulated and experimental data highly agree with the theoretical model.