Impact of Power Cell Design on RF Performance of CE and CB SiGe Power HBTs

Large-signal power performance of SiGe power HBTs are compared between common-emitter (CE) and common-base (CB) configurations with different layout structures and different unit subcells. Experiment results show that at high frequency (6 GHz), CB SiGe power HBTs have both higher small-signal and large-signal power gain values than the CE configuration. With optimization of layout and unit subcells, the power performance of both CE and CB SiGe power HBTs is significantly improved. The CB SiGe HBTs maintain the superior power gain characteristics over the CE SiGe HBTs in high frequency range, while CE SiGe HBTs become superior to CB SiGe HBTs in the low frequency range. The reasons for the device performance improvement and rules of optimizing power cell layout are discussed.