An accurate packaged model for HVHBT 120W power amplifiers and its application to 250W Doherty amplifiers

An accurate yet straightforward modeling approach is reported to develop a packaged model for InGaP/GaAs HVHBT 120 W power amplifiers (PA) at 2140 MHz. The model consists of an accurate HBT model, models for internal pre-match circuits and models for coupled bond-wire arrays. The HBT model is scaled up from an AHBT (Agilent HBT) model for a unit cell transistor. The models for the internal pre-match circuits are lumped-element equivalent circuit models derived from the EM simulated S-parameters. For high power amplifiers, the coupling between the bond-wires must be accounted for. In this work, the coupling between the bond-wires is determined up to the 4th next bond-wires. The model of 120 W PA can precisely simulate small signal S-parameters as well as large signal performances of harmonic load-pull power sweep, such as output power, P1dB, G1dB, efficiency and operation current. A very good agreement between simulation and measurement has been achieved. The model is then applied to simulate a 250 W symmetric Doherty amplifier with an efficiency above 70%. The results of simulation agrees well with the measurement. The difference in efficiency between simulation and measurement is only 1.6%.