Loop gain in analog design—A new and complete approach

Abstract

Loopgain has long been a defining function in determining stability properties of analog designs. It has surprisingly been ill defined leaving questions on loading and feedforward effects unanswered. In this article I generate a direct method for producing a unique and complete loop gain function using driving point impedance and signal flow graph techniques. In this approach loading and signal paths, feedback and feed forward paths in the amplifier as well as in the feedback net are included. Full feedback is described using two loops, the normal loop-forward amplifier-reverse feedback net loop and a reverse loop in the opposite direction, a symmetrical result.