In Learning the Art of Electronics pg.362, the author presents an op-amp follower driving a long cable. I don't understand the explanation given for the cause of oscillation. In particular, the author claims that the inductive output impedance of the op-amp (caused by weakened feedback due to op-amp dominant pole gain roll-off - not actual inductance) combined with the cable's capacitance reduces the phase margin to zero at a frequency where gain is greater than unity, causing oscillation. However, I don't understand how the closed-loop output impedance can cause oscillation.
I was under the impression that stability is determined entirely by the loop-gain, not the closed-loop gain. For instance, to analyze stability, the loop is broken (say, at the inverting terminal of the op-amp), the op-amp output is loaded with the impedance seen looking into the break point, the non-inverting input is grounded, and a signal is applied at the inverting input. The loop gain is then the negative of the gain measured at the break point. But no-where in this analysis does the op-amp output impedance appear inductive because this is not a closed-loop analysis.
How can the inductive output impedance of the closed-loop circuit (which becomes entirely resistive when the loop is opened) affect phase-margin if phase-margin depends solely on the loop-gain and not on the closed-loop gain?