I am looking at the following figure (Maxim APPLICATION NOTE 5129
Stabilize Your Transimpedance Amplifier):
I just can't understand the following: in the region half-way between fF and fi, the slope difference indicates a 180 degree phase shift between open-loop and the external network, albeit the gain is larger than unity (it is 1 only at the intersection). So, what prevents this compensated op amp from saturating to one rail in this case due to the positive feedback and over-unity gain in some frequency range ? Thanks.