A signal to be amplified is provided in polar format comprising an amplitude component (210) and a phase component (212). The amplitude component (210) is used to bias the phase component (212). The gain of amplifier (220) depends upon the bias of the signal that it receives. Therefore, the bias given to the phase component (212) provides the envelope characteristics of the output signal (224) of amplifier (220). Both (or either) of the amplitude component (210) and the phase component (212) may be predistorted (226, 310) to eliminate distortion appearing in the output signal (224).
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