Evaluation of sensitivity in transistor multiple-loop feedback amplifiers

One of the major problems in the study of feedback amplifiers is that of evaluating the sensitivity of the closed-loop gain to parameter variations. In the paper, the case of a transistor multiple-loop feedback amplifier is considered. A compact formula is developed for evaluating the sensitivity of the closed-loop gain to variations in the common-emitter short-circuit current gain hfe and input resistance hie. The method developed has the attractive feature of replacing the analysis of a complicated circuit with that of analysing a number of much simpler circuits. An illustrative example is included.