The performance of a microwave monolithic integrated circuit .（MMIC） amplifier with high output power in the Ka-band is presented. Using 75mm 0.25μm GaAs PHEMT technology provided by the Hebei Semiconductor Research Institute, this three-stage power amplifier, with a chip size of 19.25mm^2 （3.5mm × 5.5mm）, on 100μm GaAs substrate achieves a linear gain of more than 16dB in the 32.5-35.5GHz frequency range,with an average output power at 1dB gain compression of P1dB = 29. 8dBm and a maximum saturated output power of Psat = 31dBm.
