A power generator has a first plurality of power amplifiers each configured to receive a first, common supply voltage and to output a plurality of discrete DC voltages. At least one of the plurality of discrete DC voltages may be varied by varying the first, common supply voltage. The RF power generator may also include a second plurality of power amplifiers receiving a second either common or distinct supply voltage that differs from the first supply voltage. At least one of the plurality of discrete DC voltages may be varied by varying the second common or distinct supply voltage. The output of each power amplifier is added in series to generate an output voltage for the power generator. One of the plurality of power amplifiers is actuated or deactuated at a first time and an other of the plurality of power amplifiers is actuated or deactuated at a second time.