16The conditions necessary for self-sustaining oscillations to occur is a total phase shift of 360o and a total loop gain of 1. Merely having positive feedback or having a total gain of 1 or more will not guarantee self-sustaining oscillations; both conditions must simultaneously exist. As a measure of how close any feedback system is to this critical confluence of conditions, we may quantify a system’s phase margin (how many degrees of phase shift the system is away from 360o while at a loop gain of 1) and/or a system’s gain margin (how many decibels of gain the system is away from 0 dB while at a phase shift of 360o). The less phase or gain margin a feedback system has, the closer it is to a condition of instability.