Abstract: An amplifier subsystem has a modulator to generate a pair of constant amplitude phase-modulated components which are in response to an input signal, a pair of channels that include a pair of power amplifiers to amplify the components, and a combiner to combine the amplified components. A number of variable gain elements are coupled into some of a number of signal paths of the amplifier subsystem. A controller is to receive feedback from the amplifier subsystem and in response maintains signal levels of some of the signal paths within predefined ranges and controls a net gain of the linear amplifier, by adjusting the variable gain elements.