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

"Transistors are especially effective at this having very low inherent output impedence"

Yes its low but only in the forward direction. The back EMF will meet high resistance trying to go through the transistor the wrong way and then the feedback loop looks like an appetizing lower resistance path, does it not? My understanding of electronics is not so poor that I don't know the path of least resistance is the one taken. The greater the feedback the lower the resistance of the feedback loop if I am not mistaken.

"One characteristic of negative feedback is that it tends to reduce output impedence thereby more effectively dissipating reverse EMF"

Yes it reduces output impedance but how exactly? THe impedance of the device itself is a fixed value (for a given temperature and operating voltage) but high feedback makes a low impedance loop back to the input. 100% feedback is simply a wire attached from out to in and I can bet that the EMF wouldn't be disipated at the output transistors then! It seems to me that High negative feedback would simply shunt the back EMF right to the input where it will be amplified. With a tube and no feedback you have a true barrier from EMF getting back into the system. It is simply dissipated at the Plate as heat. My engineer friend told me that the same is not guaranteed with transistors because that semiconductor layer is mighty thin.


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