A modulated power supply comprises a power switching stage having at least one power switching device for generating a power signal in response to an input modulating signal. A current source is positioned in parallel with the power switching stage and continuously generates an output current. An output stage combines the power signal and the output current to form an output power supply signal. The current source supplies some, or all, of the required current at any given time. The switching device in the power switching stage either supplies the remaining required current or sinks any excess current. This has an advantage of reducing the average and peak currents flowing through the switching device, and hence the average power dissipation in the device. The output current can be set at an average (e.g. RMS) value of the current in the output power supply signal.