A system and method of generating RF includes a supply voltage source, an oscillator, an output amplifier, a load network, a peak voltage detector and a comparator circuit. The oscillator has a control signal input and an RF signal output. The output amplifier is coupled to the oscillator output. The load network is coupled between an output of the output amplifier and an output of the RF generator. The peak voltage detector is coupled across the output amplifier. The comparator circuit includes a first input coupled to the supply voltage source, a second input coupled to an output of the peak voltage detector, and a comparator output coupled to the oscillator control signal input.