TPA032D02

10-W STEREO CLASS-D AUDIO POWER AMPLIFIER

SLOS243A – DECEMBER 1999 – REVISED MARCH 2000

18

POST OFFICE BOX 655303

APPLICATION INFORMATION

class-D effect on power supply (continued)

There is a minor power supply savings with a class-D amplifier versus a linear amplifier when amplifying sine

waves. The difference is much larger when the amplifier is used strictly for music. This is because music has

much lower RMS output power levels, given the same peak output power (see Figure 10); and although linear

devices are relatively efficient at high RMS output levels, they are very inefficient at mid-to-low RMS power

levels. The standard method of comparing the peak power to RMS power for a given signal is crest factor, whose

equation is shown below. The lower RMS power for a set peak power results in a higher crest factor

Crest Factor

+ 10 log

P

PK

Time

PPK

PRMS

Figure 10. Audio Signal Showing Peak and RMS Power