Empirical global modelling of Si/SiGe heterojunction bipolar transistors

A simple and straightforward extraction procedure for a global model of silicon/silicon-germanium (Si/SiGe) heterojunction bipolar transistors (HBTs) is presented. The model has been constructed using functions that describe the dependence of the most nonlinear extracted small-signal equivalent circuit model (SSECM) parameters on the terminal voltages. The other model parameters are assumed to be voltage independent. An artificial neural network fitting tool has been used to obtain these relations. The model has been implemented in a software package without any convergence problems and has been evaluated by direct current, small-signal and large-signal network analyser measurements. An excellent correspondence has been obtained between the measurements and the output of the simulations for the extracted model. Because of its high accuracy, the model is very efficient in radio frequency circuit design. To the author´s knowledge, this is the first time that a global model for a Si/SiGe HBT has been derived directly from .a SSECM.