Class D Amplifiers Save Space, Extend Battery Life April 2005 Issue Published Date: April 04, 2005
Taking residence in nine-bump micro SMD packages, the 3W LM4670 and 2.5W LM4671 Class D audio amplifiers feature a low-power shutdown mode, enabled by driving the shutdown pin to a logic-low level. These newest members of the company’s Boomer porfolio sport externally configurable gain, which allows users to sum multiple inputs while optimizing the gain for each source. Both devices also employ unique modulation schemes that eliminate the output filter, thereby reducing external component count. They operate on a 5V supply and can drive a 4Ω load at a continuous average output of 2.3W with less than 1% THD+N. The LM4670 is optimized for push-to-talk over cellular and hands-free use. The LM4671 processes inputs via PWM and is suitable for earpiece/receiver applications as well as normal ringer and hands-free operation. Other shared features include an efficiency of 88% while operating on a 3.6V supply and driving an 8Ω load. Price for either amplifier is $0.48 each/1,000. NATIONAL SEMICONDUCTOR, Santa Clara, CA. (800) 272-9959.
