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An improved and complete method for the small-signal and high-frequency noise modeling of SiGe HBTs in a BiCMOS process is presented. A comprehensive survey of the suggested parameter-extraction methodology for the SiGe HBT transistor model in conjunction with the analytically derived equations is given. The suggested transistor model is compatible with BiCMOS processes and takes into account the parasitic effects like the extrinsic capacitances and substrate effect. The accuracy of the proposed transistor model is verified by on-wafer S-parameter measurements up to 40 GHz. An important proof of the accuracy of the proposed parameter-extraction methodology is the presented physical noise model that can accurately predict the measured noise parameters up to our measurement frequency limit of 18 GHz. The noise model accuracy at various temperatures and biases is examined. Finally, the effect of the on-wafer contact pads on the noise performance of the transistor is investigated in detail.