Amplifier circuit and methods of operation thereof

A charge pump circuit comprising:

• an input node for receiving an input voltage;
• first and second output nodes for connection to first and second reservoir capacitors and for outputting first and second output voltages respectively;
• a plurality of flying capacitor nodes;
• a network of switches for interconnecting said nodes;
• and
• a controller for operating said switches, said controller being operable in a first mode to operate said switches in a sequence of states so as to generate said first and second output voltages wherein, in said first mode, said first and second output voltages are of opposite polarity to one another and each substantially equal in magnitude to a fraction of said input voltage;
• wherein the circuit further comprises an input selector for receiving, in use, a plurality of different voltage inputs and operable to select one of said plurality of different voltage inputs as said input voltage received at the input node.

An variable power supply circuit comprising:

• a charge pump configured to output first and second supply voltages of opposite polarity;
• and
• a voltage selector for selecting one of a plurality of different voltage inputs as a selected input voltage for the charge pump;
• wherein the charge pump is configured so that a ratio of the magnitude of the first and second supply voltages to the magnitude of the selected input voltage may be controllably selected.