Accurate modeling of high frequency composite transistors for nonlinear circuits

A technique is described for developing accurate models capable of predicting small-signal scattering parameters and nonlinear operating behavior for high-frequency composite transistor circuits. This technique makes use of optimization of linearized networks for the determination of the parameters as well understood nonlinear models used in modern CAD programs. Following an explanation of the modeling technique, a flow diagram is presented which summarizes the process. Then, to demonstrate its effectiveness, the results of an application of the technique to an integrated Darlington pair which operates in the 500- to 5000-MHz range are presented.<>