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National Combines Bridge-Connected Monolithic Audio Power Amplifier, Dual Headphone Stage, Microphone Preamp and DC Volume Control in Single IC

Dec 16, 1997

December 16, 1997 - National Semiconductor Corporation® today introduced the latest addition to its line of Boomer® audio power amplifiers. The LM4834 audio power amplifier features separate driver stages for speaker and headphones, a microphone preamp, and DC volume control. This high degree of integration makes the part ideal for desktop or notebook computers.

"The LM4834 is the ideal solution for any audio system that needs to drive stereo headphones, line out, and a mono speaker with a volume control," said Shawn Scarlett, National's product marketing engineer. "It combines the best features of several existing Boomer parts, and exemplifies the product family's superior efficiency, design simplicity and quality sound."

Key advantages of the LM4834 audio power amplifier include:

  • A monolithic bridged audio power amplifier stage that generates up to 1.75W of output power into a 4-ohm speaker while consuming a minimal amount of supply current. THD (total harmonic distortion) is less than 1.0% over the audio spectrum.
  • A headphone driver that produces less than 0.1% total harmonic distortion plus noise (THD+N) when generating 70mW per channel.
  • A DC volume control that saves money by using a low-cost external potentiometer in place of a costly stereo audio-grade taper device. A control pin is available to bypass the volume control when using powered speakers or docking station.
  • An input for “system beep” that mixes into both audio channels without causing crosstalk.
  • A microphone preamp and phantom bias, integrated to save board space.
  • A power-saving shut-down/mute mode that reduces power consumption to 0.7µA (typ), extending the operating time of battery-powered systems.

Like other recent Boomer audio amplifiers from National, the LM4834 features circuitry to suppress the "pops and clicks" often associated with turn-on and turn-off. It also operates without the aid of bootstrap capacitors or snubber networks. A minimal number of external components is needed, greatly simplifying overall system design, saving board space and reducing manufacturing costs.

Price and Availability

The LM4834 is currently available in a 28-pin SSOP. In quantities of 1000, the LM4834MS (SSOP packaging) is priced at $2.25. National Semiconductor Corporation, a Fortune 500 company, produces system-on-a-chip silicon solutions for the information highway, based on its leadership in analog and mixed signal technologies. National is headquartered in Santa Clara, Calif., and focuses on the communications, personal systems and consumer markets. National has annual sales of approximately $2.5 billion and 13,000 employees worldwide. Additional company and product information is available on the World Wide Web at www.national.com.