A multi-stage radio frequency power amplifier (RFPA) includes an output stage SMPA and a driver stage SMPA. As the multi-stage RFPA operates, the magnitude of an RF switch drive signal generated by the driver stage SMPA is dynamically minimized based on I-V characteristic curves of the output stage SMPA's power transistor and the output stage SMPA's dynamically changing load line. By constraining the magnitude of the RF switch drive signal as the multi-stage RFPA operates, VGS feedthrough of the RF switch drive signal is minimized, to the extent possible. Amplitude distortion and phase distortion in the RF output that might occur due to unconstrained VGS feedthrough, particularly at low output RF power levels, are therefore avoided. Operating all stages of the multi-stage RFPA in switch mode also results in high energy efficiency and an output RF spectrum with very low wideband noise (WBN).