Interpretation of Feedback Amplifier by a Power Series of Succeeding Feedback Components

Abstract

The output of the linear feedback amplifier is modelled as the superposition of a series of succeeding feedback components. The loop circuit is interpreted as a distributed delaying circuit that spreads an instantaneously applied impulse signal into many infinitesimal components of various delay times. This interpretation is used to explain that the instantaneous feedback component is infinitesimal regardless of how large the loop gain is. Since the instantaneous loop gain between succeeding feedback components is infinitesimal, convergence of the series can be achieved. The relationship between the input and output of the overall system is then derived. We hope that our point of view can provide more insight into the operating mechanism of the feedback circuit and serve as a bridge between introductory textbooks and Nyquist's theory.