| Digital
Audio's Final Frontier-Class D Amplifier |
Digital
technology continues its march from media like CDs and DVDs toward your audio
speakers. Today, amplifiers based on digital principles are already having a profound
effect on equipment efficiency and size. They are also beginning to set the standard
for sound quality.
An
old idea, the Class D amplifier has taken on new life as equipment manufacturers
and consumers redefine the musical experience to be as likely to occur in a car,
on a personal stereo, or on an airplane as in a living room. For most consumers
today, portability and style outweigh other factors in the choice of new audio
gear.
Class
D amplifiers are ideally suited to capitalize on the trend. They are already starting
to displace conventional high-fidelity amplifiers, particularly in mobile and
portable applications, where their high efficiency and small size put them in
a class by themselves. For example, they are fast becoming the dominant technology
for entertainment systems in cars, where passengers are now apt to watch a DVD-and
expect from the vehicle's compact, ill-ventilated electronics the same rousing
surround-sound experience they get at home.
The
new amplifiers can provide it. They are typically around 90 percent efficient
at rated power, versus 65-70 percent for conventional audio amps. Such high efficiency
means, for one thing, that the amplifiers can get by with much smaller heat sinks
to carry away the energy they waste. Also, portable devices like MP3 players can
go much longer on a battery charge or can be powered by tinier, lighter batteries.
Class
D amplifiers have been used for decades in industrial and medical applications
when high efficiency is key. They have been applied with great success in devices
as small as hearing aids and as large as controllers for hefty motors and electromagnets.
They blossomed as a significant force in high-fidelity audio a few years ago,
when Class D power amplifier chips were released by companies like Tripath Technology,
Texas Instruments, and Cirrus Logic in the United States; Philips and STMicroelectronics
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