A small-signal equivalent circuit for the collector-up InGaAs/InAlAs/InP heterojunction bipolar transistor

A small-signal equivalent circuit is developed for the InGaAs/InAlAs/InP collector-up heterojunction bipolar transistor (HBT). Device S-parameters are measured in the 0.05- GHz to 40-GHz range at several bias points and used in the modeling. Parameter values are optimized for the equivalent circuit using two methods: (1) the commercial circuit analysis program Touchstone; and (2) the simulated annealing algorithm. The measured and modeled S-parameters show excellent agreement. The current gain and the maximum stable gain/maximum available gain also show very good agreement between measured and modeled values, demonstrating the validity of the model. Consistent results were obtained by two independent methods further supporting the conclusions.<
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