A radio frequency power amplifier includes a feedback control system
coupled to an input signal and a first feedback signal and configured to
provide an output; a controlled supply configured to provide power that
is controlled in accordance with a signal; and a radio frequency gain
stage powered from the controlled supply, driven by the output from the
feedback control system, and configured to provide an output signal at
the radio frequency to a resonant load, where the first feedback signal
corresponds to the output signal. Some embodiments include a sequencer in
the feedback control system and others utilize an additional feedback
loop to control the power provided by the controlled supply.