Linear and non-linear modelling verification of power HBTs

A large-signal model for power heterojunction bipolar transistors (HBTs) is described. The proposed modified Gummel-Poon model can accurately predict the DC characteristics, small-signal bias-dependent S-parameters to 40 GHz, output vs. input power (Pout vs. Pin) and load-pull responses of the HBTs operating under class A and AB bias conditions at 14 GHz. Two different sizes of Rockwell International HBTs, of emitter area 240¿m2 and 360¿ m2 respectively, have been characterized for model verification. The simulated and measured results for both devices agree well but only the responses of the larger HBT, operating in class AB, are shown here. Also, model parameter extraction and measurement techniques are discussed as a function of input power and bias, and therefore device junction temperature.