A modified Gummel-Poon model applied to HBTs

The Gummel-Poon model implemented in commercial simulators was modified to generate a large-signal model for HBTs. A representation of the thermal effects associated with the DC power dissipated by the device was added to the model and the forward transit time equation was adapted to account for the HBT transit time dependence on the base-collector voltage. The model was applied to a 1.5×20 ¿m2 AlGaAs/Gas and gave an adequate representation for the device DC characteristics for current densities up to 105 A/cm2, as well as bias-dependent S parameters up to 50 GHz. At 10 GHz the HBT output power at 1dB gain compression was predicted with less than 1dB error and the third order intercept point with less than 0.8 dB error, for class A and AB bias-points.