In inverting mode (if the input impedance of the opamp were infinite) the signal at the junction of the input resistor and the feedback resistor (the summing junction) is a *perfect* representation of the difference between the input signal and the output signal, and it is this signal that is fed into the opamp.
In the non-inverting method, the feedback signal is fed into the opamp (-) input and generally passes through at least one emitter follower before it gets to the (internal) summing junction. This means that the feedback signal is *not* a perfect representation of the output signal but it has been corrupted somewhat by passing through this emitter follower and whatever else it might find on it's way.
Something worthwhile for the GainClone crowd to consider too.
In the non-inverting method, the feedback signal is fed into the opamp (-) input and generally passes through at least one emitter follower before it gets to the (internal) summing junction. This means that the feedback signal is *not* a perfect representation of the output signal but it has been corrupted somewhat by passing through this emitter follower and whatever else it might find on it's way.
Something worthwhile for the GainClone crowd to consider too.
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