A radio frequency power amplifier has first and second amplifier stages coupled in series, one of which is operated in class F and the other is operated in inverse class F; an envelope detector adapted to detect an envelope of the input signal; a power supply coupled to supply an electrical supply voltage to the first and second amplifier stages, wherein the electrical supply voltage is controlled to follow the envelope of the input signal. Such amplifier makes it possible to maintain class F and inverse class F operation, respectively, of the first and second amplifier stages independent on the input signal. Preferably, this is done by controlling the electrical supply voltage so that the saturation levels of the first and second amplifier stages follow the envelope of the input signal.