Abstract: A monolithic power amplifier designed for 3GHz communication applications with improved gain flatness is studied based on InGaP/GaAs hetero-junction bipolar transistor technology in a commercial foundry.To improve gain flatness in a simple way,no external component was used in the real circuit except the decoupled bypass capacitors and RF choke.The measured linear gain is 23dB with gain flatness of ±0.25dB,satisfying the design goal and matching well with simulation results.This 2-stage power amplifier can deliver 31dBm linear output power and 44% power-added efficiency in the 400MHz bandwidth.The successful design with improved gain flatness is the result of superior distortion compensation and a coil model used as the RF choke.

Key words: power amplifier, MMIC, HBT