Abstract: A Ka-band continuous wave power amplifier chip is developed by utilizing 0. 15 μm Gallium Nitride power MMIC technology manufactured on silicon carbide substrates. The amplifier is designed by adopting a three-stage common source cascade structure. The 16 transistors are used for power combing, which can disperse the heat distribution. To improve output power and added efficiency, the output matching circuit is optimized by a low loss topology. The maximum gain matching is adopted for inter-stage matching, and the small signal gain flatness is also taken into account. In 28 GHz~ 30 GHz, the small signal gain is 25 dB, the continuous wave output power at 28 V bias voltage is greater than 39 dBm, the power gain is 17 dB, the additional efficiency is greater than 25% and the thermal resistance is 1. 41 ℃ /W. When the output power is 35 dBm, the IMD3 is less than -23 dBc, and the chip size is 3. 0 mm×3. 1 mm.