Improved Compact Modeling of SiGe HBT Linearity With MEXTRAM

We compare measured and simulated RF third-order distortion current, as well as the corresponding IP3, as a function of bias, for a SiGe heterojunction bipolar transistor (HBT), using MEXTRAM. The collector–base (CB) depletion capacitance model is identified to limit IP3 modeling accuracy near its peak. New CB capacitance modeling options are developed to significantly improve high-current IP3 modeling accuracy, particularly its peak behavior. Guidelines to simultaneous fitting of ${f}_{T}$ , ${f}_{\text {max}}$ , IP3, and ${C}_{\text {BC}}$ are developed.