Class D audio amp offers low power consumption, no filter

-- EDN, 4/13/2000

Class D audio amplifiers have much better efficiency than their class A, AB, or B counterparts, but they require an output filter to minimize distortion. The TPA2000D2 from Texas Instruments, however, uses an innovative PWM variation on the conventional Class D design to yield an IC that needs no inductor or capacitor filter when you use it in its targeted, short-lead-length applications. As a result, you save a few dollars and use about half the board space you previously needed for applications such as USB-connected speakers and notebook PCs.

The 2W-rms stereo amplifier with integral power FETs is available in a 24-pin TSSOP and has a noise floor as low as -75 dB. THD at 1 kHz is better than 0.07% and less than 0.5% in the 20-Hz to 20-kHz audio band. You also can select among four internal gain settings for the input preamplifiers of this IC, which has fully differential inputs. Shutown quiescent current is less than 6 mA for this single-supply device. The IC, which includes a thermal slug underneath and needs no heat sink, costs $2.50 (1000). TI also offers an evaluation system and PC-based software to let you exercise and explore the stereo amplifier's performance, along with reference designs and schematic drawings.

Texas Instruments, www.ti.com/sc/aap3788u.

-by Bill Schweber