A circuit according to the present invention improves the power supply rejection ratio for a pulse width modulated digital amplifier and can be used as a compressor and/or limiter, either in conjunction with an amplifier or independently. The circuit preferably operates by using voltage level translation to vary the amplitude of a triangle wave in response to changes in power supply voltage prior to input of the wave into a comparator of the PWM device. Because the circuit operates to improve power supply rejection, little or no distortion is introduced into the signal when used as a compressor and/or limiter. Additionally, the circuit is optionally implemented in a Class D amplifier, and provides a lower cost of implementation than conventional designs in such implementations.