Patent ID: 8854132

Claim:
A class D amplifier circuit for amplifying an input signal comprising: an H-bridge output stage comprising a plurality of switches for switchably connecting a first output to a first voltage or a second voltage and for switchably connecting a second output to said first voltage or said second voltage; and a switch controller configured to control said plurality of switches so as to vary between a plurality of states comprising at least a first state in which the first and second outputs are both connected to the first voltage and a second state in which said first and second outputs are both connected to said second voltage; wherein said switch controller is configured to vary the proportion of time spent in the first state relative to the second state based on an indication of the amplitude of the input signal; wherein the circuit further comprises first circuitry for deriving a proportion value based on said indication of the amplitude of input signal; and wherein said first circuitry comprises a translation circuit for translating an input signal to a target proportion value.