Green energy standards, the continuing need to reduce costs and
the demand for higher audio fidelity are driving the adoption of
Class D amplifiers in high-power audio applications. Traditional
analog implementations, such as Class AB topology, are more
complex and less efficient, and yet have dominated the high end
of the audio market due to their high-fidelity performance.
Class D systems are quickly narrowing this gap with simpler,
more efficient designs that offer fidelity capable of surpassing
that of analog amplifiers. A typical Class D audio system
converts audio signals at its input to a digital PWM signal,
adds power amplification in the digital domain, and then
converts the digital signal back to analog at its output. As
shown in Figure 1, the incoming audio signal is applied to a
pulse-width modulator (PWM), which consists of an operational
amplifier and a comparator. This modulator digitizes the audio
input by varying the modulator duty cycle in direct proportion
to the instantaneous value of the