The Concept of Feedback: Why We Care and Complications

Abstract

Feedback has long been used in the design of analog systems and circuits to provide system stability from variations in device parameters and in temperature. The understanding, design, and analysis of feedback systems have generally followed insight gained from consideration of ideal systems along with approximations of real systems to fit into the ideal form. This approach is not always successful in gaining understanding as loading and feedforward effects become significant. In this text, we explore an approach that reveals the intrinsic properties of feedback, allowing proper exploration to design with the direct handling of loading and of feedforward effects so that imposing simplifications and approximations early on are not needed. A unified approach is developed to general circuit analysis and to circuits including feedback in particular, in a complete and natural way that aids in developing understanding of design and of feedback systems in particular.