Patent ID: 8000821

Claim:
An audio communication unit comprising: a receiver for receiving an audio signal; a sigma-delta modulator operably coupled to the receiver, the sigma-delta modulator arranged to modulate the received audio signal, the sigma-delta modulator comprises first and second integrators each having a respective input operably coupled to a respective output of two signal subtractors, an output from the second integrator is input to an one-and-a-half bit comparator having first, second, and third output states, the one-and-a-half bit comparator provides a high pass filter response of the received audio signal to provide supply voltage immunity into the class-D power amplifier stage, and the third output state, which is a high impedance output state of the comparator, that indicates to the class-D amplifier stage to switch to an idle mode; a class-D amplifier stage operably coupled to the sigma-delta modulator, the class-D amplifier stage arranged to amplify the modulated received audio signal, and one or more feedback paths arranged from an output of the class-D amplifier stage to the two signal subtractors of the sigma-delta modulator, the one or more feedback paths provide amplified modulated signals to respective inputs of the two signal subtractors.