Rate of Closure and Phase Margin
{"Image DocumentName": "Rate of Closure and Phase Margin", "Image ImageDescription": "Relationship between the AOL and 1/Beta rate of closure and Loop-Gain (AOL B) phase margin. In a system where the rate of closure is 20dB/decade we can infer that there is at least 45degrees of phase margin remaining. This is because we can assume every amplifier circuit begins with 180 degrees of phase margin and 90 degrees is removed with the dominant low-frequency pole. Therefore if we have 90 degrees remaining for until the loop is closed and we do not want to give up more than another 45 degrees then we need to make sure that there is not a pole in AOL or zero in 1/B closer than 1 decade to the ROC. At one decade away the pole or zero that causes the phase margin to decrease will only cause an additional 45 degrees of phase shift. Using the same logic if there is a known reaction in the system that causes the phase margin to decrease by an additional 90 degrees, such as a capacitive load interacting with the Zo of the amplifier, then we must place a compensation at least 1 decade before the ROC so we can ensure the phase is boosted at least back to 45 degrees by the time the loop closes.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}