Trevithj:   The reason sources discussing the negative feedback amplifier do not mention set-points, errors, and comparators is that they have no more relevance than the stock market.  The remarks of Black are perfectly clear and also make  no mention of these factors, nor do his patents. They are understandable as he intended them- the use  of feedback bypasses  the  inadequacies of the nonlinear, variable, and uncontrollable properties of the large-gain open loop amplifier, as very easily seen in the gain analysis that shows the closed-loop gain to be set at 1/β, as fixed by a resistor divider, for example, by making the closed-loop gain 'independent entirely'' of the open-loop gain. I don't think you fully appreciate the simple algebra that governs this circuit.   
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