A method may include providing a power supply voltage to a power supply input of a power amplifier by a charge pump power supply having a select input for selecting an operating mode of the charge pump power supply, such that in a first operating mode, the power supply voltage is equal to a first voltage, and such that in a second operating mode the power supply voltage is equal to a fraction of the first voltage; wherein the power amplifier has an audio input for receiving an audio input signal, and an audio output for providing the output signal, and generates the output signal based on the audio input signal. The method may also include selecting an operating mode of the charge pump power supply based on a magnitude of the power supply voltage and a magnitude of the output signal, such that the charge pump power supply operated in the operating mode having the lowest power supply voltage in which a difference between a magnitude of the power supply voltage and a magnitude of the output signal is more than the predetermined threshold voltage.