Class D amplifiers are a type of audio amplifier that use pulse-width modulation (PWM) to convert an audio signal into a series of on-off pulses. This method allows for high efficiency, often exceeding 90%, which means they generate less heat compared to traditional amplifiers. They are commonly used in applications where power efficiency is crucial, such as in portable speakers and subwoofers. These amplifiers typically consist of a switching stage and a low-pass filter. The switching stage rapidly turns the output transistors on and off, while the low-pass filter smooths the output to produce a clean audio signal. Due to their compact size and lightweight design, Class D amplifiers are popular in home theater systems and car audio systems.