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
