[ilayn]

This is a bit of a strange presentation of stability but I liked it. I don't agree with the phase margin absence in the other comment but it would have been much clearer if the author chose to present it once via a Nyquist plot, then stuck with the magnitude plots which would clarify what we are talking about. It is also very welcome clarity to see that we are not using the weird dB unit in Bode plots.

For those who are not related to the field, what the reported subject here (and destabilizing effect of the negative feedback) is fixed by Black to remedy amp ringing, led to Bell labs, develop frequency domain techniques later analyzed by Nyquist and Bode (also seniors in Bell labs) then made western control theory kick off (then united with the Soviet techniques) and today everybody losing their mind about boosters coming back to base with SpaceX (which was already done a few times historically decades ago).