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positive feedback

n. (context physics English) a feedback loop in which the output of a system is amplified with a net positive gain and added to the input signal before the main amplifier

positive feedback

n. feedback in phase with (augmenting) the input [syn: regeneration]

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. That is, A produces more of B which in turn produces more of A. In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback. Both concepts play an important role in science and engineering, including biology, chemistry, and cybernetics.

Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect. That is, positive feedback is in phase with the input, in the sense that it adds to make the input larger. Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there will typically be exponential growth, increasing oscillations, chaotic behavior or other divergences from equilibrium. 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.

Positive feedback is used in digital electronics to force voltages away from intermediate voltages into '0' and '1' states. On the other hand, thermal runaway is a positive feedback that can destroy semiconductor junctions. Positive feedback in chemical reactions can increase the rate of reactions, and in some cases can lead to explosions. Positive feedback in mechanical design causes tipping-point, or 'over-centre', mechanisms to snap into position, for example in switches and locking pliers. Out of control, it can cause bridges to collapse. Positive feedback in economic systems can cause boom-then-bust cycles. A familiar example of positive feedback is the loud squealing or howling sound produced by audio feedback in public address systems: the microphone picks up sound from its own loudspeakers, amplifies it, and sends it through the speakers again.

Usage examples of "positive feedback".

Be durned if I'll offer any fancy explanations but-what happens when you control machinery by positive feedback?

Whenever small minorities tend to become even smaller minorities, and small majorities tend to become bigger majorities, we have a recipe for positive feedback: 'Unto every one that hath shall be given, and he shall have abundance: but from him that hath not shall be taken away even that which he hath.

There is strong evidence for positive feedback between the two hemispheres operating along the corpus callosum.

I assume that you get a positive feedback from that form or you wouldn’.

Simple linear cascades were rapidly tried out, then inhibited as stale or vis mind would have been paralyzed by positive feedback loops of hot/cold, wet/dry banality-but novel combinations of symbols were firing all the time, and if they resonated strongly enough with the current activity, their alliance could be reinforced, and even rise to consciousness.

You get a huge positive feedback effect that builds up in no time at all.

He is using broad-beam sensor sweeps to scan the region, but is not receiving any positive feedback.

Rho-class azi perform very well with positive feedback and minimal intervention, having little inclination to deviate from program.

The role of industrializationthe instrumentalization of the economic base obviously played a central and often dominant role in the instrumentalization of reason: the positive feedback loop that began to spin out of control precisely in its attempt to gain further control.

Ira, I'm suspicious of arguments by analogy-but from what I've seen over the centuries, there doesn't seem to be anything that a government can do to an economy that does not act as positive feedback, or as a brake.

One doesn't control machinery by positive feedback-at least I can't think of a case.

It was a splendid example of positive feedback in a high-gain loop.