A question about loop gain, feedback and stability of an op amp circuit
Here is a high-speed opamp (OPA211, 35MHz) with Rout of 25,000 ohms (edited up from specsheet 25 ohms). To cause oscillation, we add 1uF Cload. Rout+Cload are INSIDE the feedback loop, thus providing another 90 degrees phaseshift. Result?
Notice the 25,000 ohm Rout drops the Fring by sqrt(1,000).



For more understanding, read up on Barkhausen's 2 criteria. They relate to the Nyquist plot/point crossing.