The problem with any class-B or class-AB output stage is the difficulty of making it sufficiently linear, and there are a number of approaches. Simply reducing the output impedance so that its variations have less effect on the output voltage is one possibility, but reducing the impedance by a factor of 2 may only reduce distortion by about the same factor. Negative feedback with a loop gain of 60dB however will reduce the distortion by a factor of 1000, and so can be far more effective. Feedforward error correction is another possibility, but in this case accurate component balance would be needed to achieve distortion reduction by 60dB. Negative feedback appears to be the easiest way to reduce distortion, though of course several methods can be combined. HOME.
