Influence of Unit Subcell Selection on Small- and Large-Signal Performance of SiGe Power HBTs

The influence of unit subcell selection on the small- and large-signal performance of SiGe power HBTs is investigated. It is found that at low input power levels SiGe power HBTs using compact subcells can provide better power performance than using loose ones due to less interconnect parasitics, which is consistent with the small-signal characteristics. At high input power levels, thermal effects dominate over the parasitics effects. As a result, the loose subcells can offer better power performance than the compact ones