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1. An amplifier circuit for amplifying an input signal and outputting an output signal, said input signal being amplified by a variable gain, said gain being controlled by a received volume signal, said circuit comprising;
an amplifier for outputting said output signal; and a variable voltage power supply for supplying supply voltages to the amplifier, said supply voltages being variable based on a control signal, wherein the variable voltage power supply is a charge pump having flying capacitor terminals for connecting at least one flying capacitor and is operable, in use with just a single flying capacitor connected to said flying capacitor terminals, in first and second modes, wherein in the first mode the charge pump generates first positive and first negative supply voltages each substantially equal in magnitude to the magnitude of the input voltage and in the second mode the charge pump generates second positive and second negative output voltages each substantially equal in magnitude to half the magnitude of the input voltage, and wherein the charge pump selectively operates in said first mode or said second mode based on said control signal; wherein said control signal is based on at least one of the input signal and said received volume signal.
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