For use of criticism and punishment to modify behavior, see performance appraisal and reinforcement.
A simple negative feedback system is descriptive, for example, of some electronic amplifiers. The feedback is negative if the loop gain AB is negative.
Negative feedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other disturbances. A classic example of negative feedback is a heating system thermostat — when the temperature gets high enough, the heater is turned OFF. When the temperature gets too cold, the heat is turned back ON. In each case the "feedback" generated by the thermostat "negates" the trend.
The opposite tendency — called positive feedback — is when a trend is positively reinforced, creating amplification, such as the squealing "feedback" loop that can occur when a mic is brought too close to a speaker which is amplifying the very sounds the mic is picking up, or the runaway heating and ultimate meltdown of a nuclear reactor.
Whereas positive feedback tends to lead to instability via exponential growth, oscillation or chaotic behavior, negative feedback generally promotes stability. Negative feedback tends to promote a settling to equilibrium, and reduces the effects of perturbations. Negative feedback loops in which just the right amount of correction is applied with optimum timing, can be very stable, accurate, and responsive.
Negative feedback is widely used in mechanical and electronic engineering, and also within living organisms,[1][2] and can be seen in many other fields from chemistry and economics to physical systems such as the climate. General negative feedback systems are studied in control systems engineering.
Negative feedback loops also play an integral role in maintaining the atmospheric balance in various systems on Earth. One such feedback system is the interaction between solar radiation, cloud cover, and planet temperature.
Blood glucose levels are maintained at a constant level in the body by a negative feedback mechanism. When the blood glucose level is too high, the pancreas secretes insulin and when the level is too low, the pancreas then secretes glucagon. The flat line shown represents the homeostatic set point. The sinusoidal line represents the blood glucose level.
^
W. Ross Ashby (1957). "Chapter 12: The error-controlled regulator" (PDF). Introduction to cybernetics. Chapman & Hall Ltd.; Internet (1999). pp. 219–243.
^Robert E. Ricklefs; Gary Leon Miller (2000). "§6.1 Homeostasis depends upon negative feedback". Ecology. Macmillan. p. 92. ISBN 9780716728290.
Negativefeedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends...
positive feedback. Negativefeedback: If the signal feedback is out of phase by 180° with respect to the input signal, the feedback is called negative feedback...
Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small...
greenhouse gas emissions. Positive feedbacks amplify global warming while negativefeedbacks diminish it.: 2233 Feedbacks influence both the amount of greenhouse...
performing mathematical operations in analog computers. By using negativefeedback, an op amp circuit's characteristics (e.g. its gain, input and output...
circuits the output current is not monitored and controlled by means of negativefeedback. They are implemented by active electronic components (transistors)...
the buffer inverting inputs and ground to shunt away some of the negativefeedback; however, the single resistor R gain {\displaystyle R_{\text{gain}}}...
give a response to the signal. Feedback mechanism might involve negative and positive feedbacks. In the negativefeedback, the pathway is inhibited and...
mechanical contact bounce in switches. They are also used in closed loop negativefeedback configurations to implement relaxation oscillators, used in function...
are viewed as complex dynamical systems. The study of positive and negativefeedback processes, attractors and system dimensionality, phase transitions...
only with global feedback loops. Design architectures with local feedback can be used to compensate the lack of global negativefeedback magnitude. Design...
series negativefeedback (op-amp follower, non-inverting amplifier, etc.), where one input is used for the input signal, the other for the feedback signal...
through upstream elements, this is canonically negativefeedback (red blunt arrow). A negativefeedback loop is also known as a balancing loop, and it...
it impossible to build a plant with exactly the right capacity. A negativefeedback loop slows down a process, tending to promote stability. The loop...
resolution in policy debate Negativefeedback, a feedback loop that responds in the opposite direction to a perturbation Negative liberty, freedom from interference...
In the physiology of the kidney, tubuloglomerular feedback (TGF) is a feedback system inside the kidneys. Within each nephron, information from the renal...
Cybernetics is the transdisciplinary study of circular processes such as feedback systems where outputs are also inputs. It is concerned with general principles...
response to specific biochemical signals and is often subject to negativefeedback regulation. For instance, high blood sugar (serum glucose concentration)...
revolutionized the field of applied electronics by inventing the negativefeedback amplifier in 1927. To some, his invention is considered the most important...
positive feedback can have negative differential resistance. These are used in oscillators and active filters. Because they are nonlinear, negative resistance...
the production of molecules that are no longer needed. This type of negativefeedback is an important way to maintain balance in a cell. Enzyme inhibitors...
Negging ("to neg", meaning "negativefeedback") is an act of emotional manipulation whereby a person makes a deliberate backhanded compliment or otherwise...
optimised for use with negativefeedback, and this article discusses only negative-feedback applications. When positive feedback is required, a comparator...
interested in Harold Stephen Black's work on negativefeedback, so he held a graduate seminar on negativefeedback. Bill Hewlett attended the seminar. Scott's...
years. Each glacial period is subject to positive feedback which makes it more severe, and negativefeedback which mitigates and (in all cases so far) eventually...
since at these frequencies feedback oscillators perform poorly due to excessive phase shift in the feedback path. In negative-resistance oscillators, a...
Global Information
