Intermodulation characteristics of UHV/CVD SiGe HBTs

Extensive SPICE circuit simulations were performed to explore the physics underlying the unusually high linearity (15 dBc OIP3/P/sub DC/) observed in SiGe HBT's. The EB and CB depletion capacitances were found to be the major contributors to the observed high linearity. Both the absolute value and the bias dependence of the depletion capacitances contribute to nonlinearity, while the diffusion capacitance has negligible impact.