Class-D amplifier

From Wikiants

A switching amplifier or class-D amplifier is a electronic amplifier which, in contrast to the active resistance used in linear mode AB-class amplifiers, uses switching mode of transistor to regulate power delivery. The amplifier, therefore, features the high power efficiency (low energy losses), which additionally results in lower weight by eliminating the bulky heat sinks. Additionally, if voltage conversion is necessary, the on-the-way high switching frequency allows to replace the the bulky audio transformers by small inductors. Low pass LC-filtering smoothes the pulses out and restores the signal shape on the load.

Class D amplifiers are often used in sound reinforcement system power amplifiers, where a high output is required. The Crest Audio CD3000^[1], for example, is a Class D power amplifier that is rated at 1500 watts per channel, yet it weighs only 21 kg. A small number of high-output bass amplifiers also use Class D amplification technology, such as the Yamaha BBT 500H ^[2] bass amplifier which is rated at 500 watts, and yet it weighs less than 5 kg.

The term "Class-D" is sometimes misunderstood as meaning a "digital" amplifier. The quantization of the output signal at the power stage can be controlled by either an analog signal or a digital signal. Only in the latter case would an amplifier be using fully digital amplification.