Distortion in Feedback Amplifiers

Distortion in feedback amplifiers and other non-linear circuits is analyzed for the case where the magnitude and phase of the feedback varies with frequency. The analysis is limited to cases where the distortion products are small compared to the fundamentals and where the non-linear element can be described by a power series having only a few terms. However, many practical amplifiers are adequately described by the analysis. Formulae are derived for a number of third-order products and their dependence upon various feedbacks at second order frequencies is demonstrated.