Envelope following voltage converter

A power supply system 100 includes a voltage converter which generates a first voltage at an output node Vout, and an envelope-follower circuit which generates a second voltage associated with the envelope of a radio frequency signal. The system combines the second voltage with the first voltage, e.g. via a capacitor CB, to provide an output voltage PA_Vcc for an RF power amplifier. The output voltage has a waveform that follows the peaks of an envelope of the RF signal. The voltage converter may comprise an inductor LB and switches S1 and S2 and may operate as a boost converter. Alternatively, the switches S1 and S2 may be positioned for a straight-through connection of the battery input voltage Vin to the node Vout. Alternatively, the switches S1 and S2 may both be opened and a reduced voltage supplied to node Vout via circuit 104 and switch S3.