A supply modulator is provided, having a first amplifier circuit configured to generate a first electrical signal, a second amplifier circuit configured to generate a second electrical signal, the first and second electrical signals being for driving an electrical load, and a control circuit electrically coupled to the first and second amplifier circuits wherein the control circuit is configured to generate a pulsed electrical signal and to supply an output control signal to the second amplifier circuit for controlling generation of the second electrical output signal, wherein the supply modulator is configured to operate in two modes of operation, for the first amplifier circuit to generate the first electrical signals in response to quiescent current of the first amplifier circuit, for the control circuit to generate a modulated electrical signal in accordance with a clock signal in one mode, and, for the second amplifier circuit to operate.