Radio frequency power amplifier (RF PA) is an important component of various wireless transmitters. In the front circuit of the transmitter, the RF signal power generated by the modulating oscillation circuit is very small, and it needs to go through a series of amplification of a buffer stage, an intermediate amplifier stage, and a final power amplifier stage to obtain enough RF power before it can be fed to the antenna to radiate out. In order to obtain enough RF output power, it is necessary to use RF power amplifier.