Modeling and characterization of HBT linear power amplifier for PCS applications using an internal node probing technique

This work was involved in the large-signal modeling and characterizations of linear monolithic microwave integrated circuits (MMIC) heterojunction bipolar transistor (HBT) power amplifier for personal communications services (PCS) applications by using an internal node probing technique as a too]. As the first step to obtain an accurate large-signal model, small-signal modeling based on the T-model equivalent circuit was carried out. The uniqueness of current approach is that it determined all the eight intrinsic parameters of smallsignal model analytically without any simplification. Decent agreements between the small-signal model and the measured S-parameters verified the accuracies of the model, which were further validated in terms of bias-dependencies of extracted intrinsic parameters.; Based on standard Gummel-Poon model, large-signal modeling including self-heating effects was performed. The model was then compared with the measurement in terms of dc iv, small-signal S-parameters, and large-signal power performances including waveform. measurement. The excellent agreement between the model and the measurement proved the validity of large-signal model. In terms of internal node probing technique a new probe with higher bandwidth and less resonance has been developed and it has been shown that it can be accurately modeled by a simple R-C network whose equivalent circuit parameters would be further utilized to improve the probe bandwidth. The present technique proved a valuable tool to verify a circuit design. Finally, the large-signal power amplifier model was thoroughly verified against the measurements in terms of power performances, dependencies on the frequency and the dc power supplies, and ultimately internal-node waveforms for the first time.