A Heterojunction Bipolar Transistor Large-signal Model Focused on the Saturation Region

We present a new large signal model of HBT for accurately fitting IC-VCE curves at the saturation region. Because of the highly doped base of HBT, the collector is high-level injected in the region. This model treats the high-level injected collector as an effective base width widening and the saturation current terms of Ebers-Moll model are modified accordingly. A new empirical function is used to describe the base width variation. The simulation results using the model follow the measured IC-VCE curves at the saturation region very well. For verification, this model is applied to a multi-finger HBT and load-pull simulation results based on the model are compared with measured ones.