High frequency AC equivalent circuit model of Si/SiGe HBTs

In applications based on Si/SiGe HBTs, the veracity of the AC equivalent circuit model is the key element during circuit design. To avoid errors in available ranges for bipolar devices from f_β to f_T, we developed a novel model with accurate circuit form by derivation of I-V equations and circuit descriptions of Y and H type AC parameters. The novel HBTs´ model represents ΔE _g between two sides of heterojunction, and legible differences with BJTs in capacitance proportion caused by decreasement of emitter base doping rate and in the ratio to capacitance and resistance by the reduction of base width. Results of these differences make the novel model´s circuit form varies from BJTs´ in high frequency ranges