Positive feedback

Positive feedback is a process that occurs in a feedback loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation.[1] That is, A produces more of B which in turn produces more of A.[2] In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback.[1][3] Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect.[1][3] That is, positive feedback is in phase with the input, in the sense that it adds to make the input larger.[4][5] Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillations or divergences from equilibrium.[3] System parameters will typically accelerate towards extreme values, which may damage or destroy the system, or may end with the system latched into a new stable state. Positive feedback may be controlled by signals in the system being filtered, damped, or limited, or it can be cancelled or reduced by adding negative feedback.