Generalised high-frequency network theory of field-effect transistors

Abstract

The paper is concerned with calculation of the small-signal admittance parameters of field-effect transistors in general. For this purpose, it is first shown that field-effect transistors can be effectively treated as a special class of analogue RC transmission lines, in which the resistance is uniformly distributed but the capacitance is nonuniformly distributed. The difficulty of analysing this type of transmission line is resolved by assuming piecewise uniformity as a good first-order approximation. The matrix method of analysis is employed. This has been found to be a simple and rapid means of calculating admittance parameters of field-effect transistors in a closed analytical form, which is particularly suitable for practical circuit analyses. These parameters lead naturally to the appropriate representation of device characteristics by equivalent circuits, valid over their entire useful frequency range. Calculation of both the forward- and reverse-transmission parameters under saturated-drain-current conditions has been the main object of the analysis, which is, however, in general terms throughout.