National Semiconductor Raises Power Output From Boomer® Audio Amplifiers for PC Headphones or Speakers

January 30, 1998 - National Semiconductor Corporation® today announced availability of the latest generation of Boomer audio amplifiers. The LM4870 and LM4871 are bridge-connected amplifiers specifically designed for laptop or desktop computer sound systems. Both can alternately drive stereo headphones or stereo speakers with up to 1.1W output (8 ohms, 0.5%THD) as a speaker driver. Although the two parts are similar, the LM4870 also provides a status flag and amplifier muting when headphones are plugged into the system. Both devices feature superior output power and sound quality from low-voltage supplies down to 2.0V with no degradation in performance.

"This latest series of popular Boomer power amps offers greater efficiency and higher quality sound at a lower price than our previous design" said Shawn Scarlett, National's technical marketing engineer. "Unlike our competitors, our ratings are specified over the entire audio range, our performance is superior on low impedance loads (4 ohms) and devices reach shutdown current immediately," he added.

Like previous Boomer designs, both parts incorporate a shutdown mode that reduces supply current consumption to less than one microamp (typ). This eliminates the need for an external FET, saving the designer both board space and cost. An internal thermal shutdown mechanism protects the device from overheating, making it virtually indestructible.

Like other recent Boomer audio amplifiers from National, the LM4870 and LM4871 feature circuitry to suppress the"pops and clicks" often associated with turn-on or turn-off. Both parts operate without the aid of bootstrap capacitors or snubber networks. A minimal number of external components, combined with the products' small footprint, greatly simplifies overall system design, saves board space and lowers manufacturing costs.

The LM4870 is currently available in a 16-pin SOIC package designated LM4870M. The LM4871 is offered in either an 8-pin small surface-mount package (SOIC) designated LM4871M, or an 8-pin dual in-line packages (DIP), designated LM4871N. In quantities of 1000, the LM4870 is priced at $1.00 in either package. The LM4871 is also priced at $1.00 in either package, in quantities of 1000.

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, California, 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.