For battery operated devices, this class D amplifier is suitable because its high efficiency (85%) helps extend the battery life. In the internal circuitry, a boost converter  with over 90% efficiency is provided to step-up the voltage supply, and need only one external inductor as the additional component for this function. When driving 8 ohm loud speaker, this class-D amplifier circuit gives 1.5W output power with 3.6 voltage supply. Here is the schematic diagram of the circuit:

low voltage class d amplifier circuit schematic

The amplifier’s PWM and the supply booster PWM is internaly synchronized, thus eliminating beat frequency noises from the PWM stage. The gain control pin can be pulled to Vcc, floated, or grounded to set the gain to 2V/V,  6V/V, or 10V/V. The input stage of this class-D amplifier chip has internal low-pas filter to ensure the anti-aliasing between the input signal and the PWM frequency. This circuit works with 2.5 to 5.5 supply voltage, suitable for hand-helds or any battery-powered application. [Circuit’s schematic diagram source: Texas Instruments Application Notes]