Improved closed-form expressions for S-parameters of BJTs using modified Gummel-Poon model

Noticeable differences particularly in phase were observed when closed-form expressions reported earlier were employed to predict small-signal S-parameters for the packaged devices. With improved close-form expressions presented in this paper, the overall situation both in terms of magnitude and phase has improved significantly by adding extrinsic base-to-collector capacitance. The difference in magnitude between measured and predicted using a modified Gummel-Poon model has reduced from 4 dB to less than 2 dB. The error between measure and calculated phase is no more than 8 degrees at any point whereas the expressions based on the intrinsic model greatly underestimated the phase for packaged devices