文档介绍：STANDARD LINEAR IC S
Trends in class D
amplifiers
Improving audio quality and system
performance with digital amplifiers
BY SEAN DAVIS fixed-carrier frequency. The resulting width, without changing the origi-
Cirrus Logic signal is a fixed-carrier frequency nal audio content. An effective way
Austin, TX (usually in the hundreds of kilo- to correct for the high EMI of tradi-
hertz) of varying pulse width. High- tional PWM modulators is to vary
er-voltage power MOSFETs are then both edges of the switching PWM
odern class D solutions used to amplify this PWM signal. signal, as shown in Fig. 1.
have vastly improved over The amplified PWM signal goes The signal is centered on the carri-
M previous generations, as de- through a low-pass filter, thereby re- er frequency, but neither edge is
signers of these systems have made moving the carrier frequency and re- repetitive cycle to cycle. This has the
great strides to improve system ro- covering the original baseband au- benefit of maintaining a constant-
bustness and increase audio quality. dio signal. carrier frequency, but because the
In fact, the advantages of using these While this topology is effective, it edges are not switching at a constant
amplifiers now outweigh any disad- results in some unwanted artifacts, rate, the radiated energy at the carri-
vantages associated with them for such as high amou