All operational amplifier (op-amp) datasheets have an input voltage range limitation called the common-mode range. Strictly speaking, the common-mode voltage is the average voltage on the two inputs ...

The almost universal choice in semiconductor power amplifiers is for a unity gain output stage, and specifically a voltage follower. Output stages with gain are not unknown, 1 but they are not common.

Fig 1. This shows the spectra of both waveforms when the Class D output is issuing silence (no audio, duty cycle = 50%) with a switching frequency of 333 kHz. Fig 2. The blue line shows the energy ...