Sigma-delta class D amplifier for CD player

摘要

The amplifier contains a loop filter, a clocked comparator, and a switching end stage in a forward branch, while a feedback branch leads from the end stage to a summator in front of the loop filter, with the summator subtracting the feedback signal from the applied input signal. The power stage output signal is fed via a low pass filter to the load. A suppressed carrier (SC) loop filter is used for direct processing digital input signals, while the feedback branch includes an antialiasing filter. The digital input signal is fed to the summator via an SDM. The clock pulse frequency (fT2) of the SC loop filter is at least twice as high as that (fT1) of the comparator.