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Re: What happens to back EMF with a feedback amplifier?

Just the opposite.

since the output stage of an amplifier is very low impedence compared to the impdence of the feedback loop, the energy from loudspeaker reverse EMF is almost entirely dissipated in the output devices. Transistors are especially effective at this having very low inherent output impedence. The voltage resulting from reverse EMF is seen as a component of the error signal and is compensated for in the feedback loop. Depending on how effectively the feedback circuit is designed, it could add to or subtract from distortion so it is impossible to generalize but in a well designed feedback loop, the feedback will compensate by working against the error. One characteristic of negative feedback is that it tends to reduce output impedence thereby more effectively dissipating reverse EMF. Without negative feedback, the reverse EMF just adds to or subtracts from the bias voltage applied to the output device increasing distortion and FR nonlinearity.

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