The LM4674 stereo Class D audio power amplifier features a filterless modulation scheme that reduces external component count, conserving board space and reducing system cost. The outputs of the device transition from V_DD to GND with a 300kHz switching frequency. With no signal applied, the outputs for each channel switch with a 50% duty cycle, in phase, causing the two outputs to cancel. This cancellation results in no net voltage across the speaker, thus there is no current to the load in the idle state.

With the input signal applied, the duty cycle (pulse width) of the LM4674 outputs changes. For increasing output voltage, the duty cycle of the A output increases, while the duty cycle of the B output decreases for each channel. For decreasing output voltages, the converse occurs. The difference between the two pulse widths yields the differential output voltage.