What angle did you have in mind, and why should we follow your intuition?While determining the phase cross over frequency, why is it taken at -180degrees only? why not any other angle?
Good explanation.Most feedback circuits use an amplifier with inverting gain and this yields 180 degrees phase shift. If the feedback circuit contributes another 180 degrees phase shift, the total circuit phase shift is 360 degrees, otherwise the feedback is in phase and the circuit will oscillate if the gain is high enough. Thus, the 180 degree phase point is critical because it is the point at which oscillation occurs, but after 135 degrees phase shift the output becomes subject ringing etc. so the range between 135 and 180 degrees phase shift is often looked at in detail, but that is something you will probably learn in another class.
Remember, oscillation always occurs when the phase shift reaches 180 degrees if the gain is equal to or greater than one. When the gain is greater than one the circuit distorts the signal to drive the gain back to one.
http://www.ti.com/lit/an/snva020a/snva020a.pdfWhile determining the phase cross over frequency, why is it taken at -180degrees only? why not any other angle?
by Jake Hertz
by Jake Hertz
by Duane Benson
by Duane Benson