A systematic approach to the analysis of general and feedback circuits and systems using signal flow graphs and driving-point impedance

Feedback has long been a mysterious effect that has either fixed or ruined circuits. Phase- and loop-gain analysis have served to maintain this view of feedback by being difficult to handle and to interpret. In this paper, a unified approach to circuit analysis is presented which readily handles feedback circuits using driving-point impedance (DPI) techniques to directly generate a signal flow graph (SFG). When coupled with pole-zero diagrams, a complete analytical tool results, giving the design engineer qualitative as well as quantitative answers. A simple extrapolation of the methodology shows it to be applicable to systems composed of linear cells such as active filters, where loading effects at input and output ports are automatically included in the analysis.