Demand for a variety of handheld consumer electronics products is resulting in an onslaught of audio power amplifiers from companies like Austriamicrosystems,
National Semiconductor, STMicroelectronics, Toshiba America Electronic Components and Texas Instruments.
These amplifiers some filterless, some Class
D, Class AB and even Class-KB for automotive audio applications can operate over a wide voltage range, deliver high output power and enable longer battery life.
Applications include MP3, CD/DVD and video players, mobile phones, personal digital assistants and other handheld, battery-powered systems, as well as
STMicroelectronics (Geneva) is offering a filterless Class D amp that is said to provide higher audio power output while preserving and extending battery life. The TS4962 amplifier for gaming, polyphonic ringers and speaker phones, as well as PDAs and laptops, provides 3 watts of output power into a 4-ohm loudspeaker when operating on a 5-volt power supply. Its quiescent current with no input signal is 2.3 milliamps typical, and standby current is 10 nA when the amp is powered down using its active-low control line.
The latest single-channel audio amplifiers from Austriamicrosystems AG (Unterpremstaetten, Austria) deliver 1.6 W of output power at comparable distortion levels, or lower distortion levels at comparable output power, than similar products, the company said. The AS1701 and AS1706 amps contain a bridge-tied load (BTL) output stage to differentially drive 4-ohm and 8-ohm speakers. The amplifiers provide 0.05 percent total harmonic distortion plus noise (THD+N) at 1-W output power into an 8-ohm load. At THD+N of 1 percent, they
deliver 1.6 W of output power into a 4-ohm load or 1.2 W into an 8-ohm load. Due to the wide input supply range of 2.7 to 5.5 V, the amplifiers can be used for 3-V
systems as well, delivering 600 mW of continuous output power into 4 ohms.
National Semiconductor Corp. (Santa Clara, Calif.) has rolled out a tiny, 1.4 x 1.4-mm, 2.5-W, Class D audio amplifier as well as a high-output-power stereo
Class D amplifier. Both Boomer devices, which are filterless, provide high-quality output power with a minimal number of external components, according to National. The 1.4 x 1.4-mm LM4673 mono Class D amplifier comes in a 0.4 mm-pitch micro-SMD package. The stereo LM4674 Class D amp also provides board space efficiency for stereo applications in a 2 x 2-mm, 0-5-mm-pitch package.
Toshiba America Electronic Components Inc. (San Jose, Calif.), meanwhile, has introduced a Class-KB (keyed bridge-tied load) audio power amplifier based on
bipolar CMOS and double-diffused MOS technology. Designated TB2905HQ, the linear audio amplifier is for car-audio systems, including CD, DVD and navigation
applications. The device, which incorporates four BTL amplifier channels, boasts many built-in functions including standby switching, muting, offset and clipping
detection, and various protective circuits.
The TPA3200D1 digital-input Class D audio power amplifier from Texas Instruments Inc. (Dallas) is said to enable development of flat-panel displays with superior
sound quality, while minimizing cost and component count. Suited for 27-inch and larger displays, the digital amplifier operates more efficiently than traditional linear amplifiers, minimizing heat and eliminating the space
required for an external heat sink, according to TI. The amplifier operates from 8- to 18-V supply voltages and has THD+N of less than 1 percent (0.09 percent at
1 kHz) at half the rated output power level, and less than 10 percent THD+N at the maximum rated output level.
Maxim Integrated Products Inc. (Sunnyvale, Calif.) has rolled out an integrated 2-W Class AB audio amplifier for notebook PCs, small flat-panel displays and portable DVD/media players. The MAX9756 is said to boost output power while minimizing distortion. It features Maxim's automatic level control, which increases average output power while reducing distortion and protecting the loudspeakers. The amplifier combines a 150-mA low-dropout regulator with Maxim's DirectDrive headphone amplifier technology.