Abstract: To address the critical demand for high power and high efficiency radio frequency power amplifiers in radar systems, an gallium nitride internally matching power amplifier operating in the C-band is designed. The input and output are matched using chip capacitors and bond wires machined on an Al₂O₃ ceramic substrate. The designed internal matching power amplifier operates with a drain voltage of 48 V and a gate voltage of -2 V, at 5.7 GHz~5.9 GHz, the maxium output power is 47.6 dBm, the PAE is greater than 40%, and the power gain is greater than 12.8 dB. It fully shows the characteristics of gallium nitride high electron mobility transistor devices with high withstand voltage and high output power.