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Encyclopedia > Positive feedback loop

Positive feedback is a type of feedback. Open systems (ecological, biological, social) contain many types of regulatory systems, among which are systems that involve positive feedback and its relative negative feedback. In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. ... An open system is one whose border is permeable to energy (or mass) as distinct from a closed system in which the border is not permeable. ... Negative feedback is a type of feedback, during which a system responds so as to reverse the direction of change. ...

When a change of variable occurs in a system, the system responds. In the case of positive feedback the response of the system is to change that variable even more in the same direction. For a simple example, imagine an ecosystem with only one species and an unlimited amount of food. The population will grow at a rate proportional to the current population, which leads to positive feedback. This has a de-stabilizing effect, so left unchecked, does not result in homeostasis. In some cases (if not controlled by negative feedback), a positive feedback loop can run out of control, and can result in the collapse of the system. This is called vicious circle, or in Latin circulus vitiosus. The word proportionality may have one of a number of meanings: In mathematics, proportionality is a mathematical relation between two quantities. ... Homeostasis or homoeostasis is the property of an open system, especially living organisms, to regulate its internal environment so as to maintain a stable condition, by means of multiple dynamic equilibrium adjustments controlled by interrelated regulation mechanisms. ...

Positive and negative do not mean or imply desirability. The negative feedback loop tends to slow down a process, while the positive feedback loop tends to speed it up. Positive feedback is used in certain situations where rapid change is desirable.

One common example of positive feedback is the network effect, where more people are encouraged to join a network the larger that network becomes. The result is that the network grows more and more quickly over time. The network effect causes a good or service to have a value to a potential customer dependent on the number of customers already owning that good or using that service. ...


In electrical engineering

Feedback is well understood and widely studied in electrical engineering. Whereas negative feedback is used to stabilize the response of an electrical system and reduce nonlinear effects, positive feedback is often used to take advantage of these nonlinear effects (for example, the Schmitt trigger), or at least is used with the understanding that nonlinear effects, not feedback, will limit the output (in oscillators, and in popular configurations for MESFET amplifiers). An important consideration in the design of feedback amplifiers is to avoid unintentionally creating positive feedback (see frequency compensation). Positive feedback from loudspeakers to a microphone causes the familiar squealing sound. Electrical engineering is an engineering discipline that deals with the study and application of electricity and electromagnetism. ... To do: 20th century mathematics chaos theory, fractals Lyapunov stability and non-linear control systems non-linear video editing See also: Aleksandr Mikhailovich Lyapunov Dynamical system External links http://www. ... In electronics, a Schmitt trigger is a special kind of comparator circuit. ... Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... The MOSFET, or Metal-Oxide-Semiconductor Field-Effect Transistor, is by far the most common field effect transistor in both digital and analog circuits. ... An amplifier is a device which changes a small movement into a larger movement. ... A feedback amplifier, also known as negative feedback amplifier is an amplifier which uses a feedback network, generally for improving performance (gain stability, linearity, frequency response etc. ... In electrical engineering, frequency compensation is a design technique for amplifiers which use negative feedback or those, such as operational amplifiers, that are intended for use with negative feedback. ... Closeup of a loudspeaker driver A loudspeaker is a device which converts an electrical signal into sound. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ...

In gaming

In games, positive feedback is a critical and heavily exploited mechanism for controlling the resources in a game. It has a number of uses: A game is a recreational activity involving one or more players, defined by a) a goal that the players try to reach, and b) some set of rules that determines what the players can do. ...

  • To speed up a game that would otherwise be too slow. For example, if the annual income did not increase in SimCity as the city grew, it would take many years to earn enough money to fill the large map with structures.
  • To create a feeling of growth and progress. For example, in a role-playing game, it's typical for players to struggle with enemies near the beginning that later become easy to destroy due to enhanced strength and weapons, purchased with the experience and gold earned by those early encounters.
  • To magnify small advantages. For example, in Starcraft, a player who has more resources will be able to build more units, enabling them to seize more resource-rich territory and so gain yet more resources. This allows a player with a small resource advantage to crush their opponent in time.

However, accidental positive feedback loops in games can also be a source of degenerate strategies, destroying the game's challenge. For example, suppose a player in a first-person shooter gained 100 health points for every person they killed. Then, a careful player could quickly amass a large number of health points and become virtually indestructible. SimCity is a real-time strategy/simulation computer game (or software toy). It is game developer Maxis flagship product. ... A role-playing game (RPG) is a type of game where players assume the roles of fictional characters via role-playing. ... StarCraft StarCraft (SC) is a real-time strategy computer game produced by Blizzard Entertainment in 1998. ...


  • Katie Salen and Eric Zimmerman. Rules of Play. MIT Press. 2004. ISBN 0262240459. Chapter 18: Games as Cybernetic Systems.

Categories: University book publishers | Stub ...

See also

  Results from FactBites:
Feedback - Free Encyclopedia (814 words)
Feedback may be negative, thus tending to reduce output, or positive, thus increasing output.
Positive feedback amplifies possibilities of divergences (evolution, change of goals); it is the condition to change, evolution, growth; it gives the system the ability to access new points of equilibrium.
For example, in an organism, most positive feedbacks provide for fast autoexcitation of elements of endocrine and nervous systems (in particular, in stress responses conditions) and play a key role in regulation of morphogenesis, growth, and development of organs, all processes which are in essence a rapid escape from the initial state.
  More results at FactBites »



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