A generalized theory of transistor bias circuits

ONE of the important problems met in the design of transistor circuits is how to arrange the bias network to obtain the proper operating point and how to maintain this condition within specified limits, subject to environmental changes such as temperature, or to a range of parameters due to production spread in device manufacture. Several bias circuits have been proposed and are being used which give good performance. The question naturally arises as to what essential features do these circuits have in common? It is the purpose of this paper to introduce a very general method of analyzing bias circuits and begins by first showing that almost all 3-terminal bias circuits can be reduced to the same simple standard form. The analysis for this standard-form circuit will then be presented. Finally, an example drawn from current practice will be given showing the unifying concepts which result from the general theory.