A class-D pulse width modulated amplifier. The amplifier includes a current switch, an integrator and a comparator connected in a feedback loop. The feedback loop generates an ultrasonic frequency carrier which is utilized in the pulse width modulation of an audio input signal. In one embodiment a current switch and an audio input source are in electrical communication with an integrator. The output signal of the integrator is the input signal to a phase split differential output comparator having hysteresis. The differential output signals of the comparator are the input signals both to a load and to the current switch, thereby completing the feedback loop. In one embodiment the current switch includes compression circuitry.