PWM Motor Speed Control Using Class D Audio Amplifier

This is class D audio amplifier circuit that is used to control PWM motor speed. This circuit has two advantages for battery-powered portable devices. First, this circuit produces much less power dissipation than do it’s linear cousins. Second, it enhances battery life. Here is the circuit:

A potentiometer (R2) is used to generate a variable DC voltage. To match the input range of U1, the potentiometer is biased by resistor R1. To maximum-speed reverse rotation of the motor, the pot must be rotated full counter-clockwise, and to produces maximum-speed forward rotation in the motor, the pot must be rotated full clockwise. Mid-scale on the pot corresponds to motor off. To reduce EMI, the filter should be included. [Source: Maxim Application Note]