Improved approach for determination of pad model parameters for SiGe HBT

A new method for determining the pad parasitic elements of Si-based devices is presented. Comparison between the new method and approximation method shows that the parasitic elements of the pad extracted by linear fitting method presented in this paper is more accurate. Once the pad parameters are obtained, small-signal equivalent circuit parameters of SiGe HBT implemented with AMS 0.35 μm BiCOMS technology are extracted. The extrinsic resistances are determined under 'over drive I_B' bias condition, and the intrinsic elements are all calculated by using analytical method. Good agreement is achieved between simulated and measured results of the transistor over the test frequency range.