Does the following simple test deduced from Nyquist criterion also apply to positive feedback case or it needs to be modified?
If magnitude of loop gain i.e. |T (jω)| > 1 at the frequency where phase(T (jω))= −180◦, then the amplifier is unstable.
Reference:Analysis and Design of Analog Integrated Circuits, 5th Edition http://fa.ee.sut.ac.ir/Downloads/Ac...sign_of_Analog_Integrated_Circuits_5th_ed.pdf, pg 628 2nd last paragraph
https://www.allaboutcircuits.com/te...ve-feedback-part-4-introduction-to-stability/