Designing with Class D amplifier ICs

CLASS D audio amplification is becoming the solution of choice in consumer audio, by enabling long battery life and compact dimensions. However, designers must take care to avoid complexity elsewhere in the system, including the power supply, output filtering and input signal conditioning.

The switching amplifier, or Class D amplifier, has risen quickly to prominence in consumer audio applications, from MP3 devices including mobile phone handsets to games consoles, LCD-TVs and home cinema. The ace in the pack for Class D is its vastly superior efficiency, which can be as high as 85-90 percent in practice. A linear Class AB implementation will normally achieve around 25 percent at typical listening levels.

In handheld applications the low power dissipation of Class D allows designers to combine high audio performance with a long battery recharge interval. Battery life is a key figure of merit for all personal communication and audio devices. For mains powered equipment, such as audio-visual (AV) products and games consoles, the high power efficiency of Class D brings the advantage of reduced heat dissipation.

Hence designers can specify smaller heatsinks, to achieve lower profile styles as well as lower bill of materials and assembly costs. In fact, careful design of the power supply can allow heatsink-less operation up to several Watts per channel of output power.