A fully integrated broadband analog power amplifier (PA) based on GaN 250nm process is proposed. Based on the differential structure of transformer coupling, by using magnetically coupled resonator (MCR) broadband matching technology and multi-peak gain superposition technology, the bandwidth of the PA is expanded, so that the PA can achieve a peak output power (P out ) of > 5W in the bandwidth range of 2.5-5GHz. The relative bandwidth of the PA is 81%. In the 2.5-5GHz frequency band, the proposed PA achieves a peak P out of 38.5dBm, with a peak PAE of 48.6%, exhibiting excellent broadband performance.