Digital class-D audio amplifier

Audio amplifiers have been manufactured using class-A and class A-B configurations since the earliest days of radio. These amplifiers are the simplest to implement and have been manufactured using vacuum tubes and transistors. These class A and class A-B amplifiers, while simple and easy to manufacture, are inefficient. Their output stages operate at about 40% efficiency. resulting in heat generation. This means that for each 100 watts of input power, they only put out about 40W. A Class-D audio amplifier is disclosed which accepts a digitized audio signal input and drives a load such as a loudspeaker without digital-to-analog conversion. The amplifier preferably comprises (1) means for processing a plurality of digital audio input values to create a plurality of deviation values respectively based on the deviation of the input value's relationship from a previous audio input value, (2) means for producing a carrier signal, (3) modulation means for using the deviation values to responsively modulate the carrier signal by varying the frequency of its waveform inversely with the magnitudes of the deviation values, and (4) filter means operative on the modulated carrier to produce an analog voltage capable of driving the load.