A positive feedback system is a process where the effects of a perturbation on a system include an increase in the magnitude of the perturbation. It is also known as exacerbating feedback or self-reinforcing feedback. In contrast, negative feedback reduces or counteracts the original stimulus.
Key Facts
- Definition: Positive feedback is a process that occurs in a feedback loop where the effects of a perturbation on a system include an increase in the magnitude of the perturbation. It is also known as exacerbating feedback or self-reinforcing feedback.
- Amplification: In a positive feedback system, the original stimulus is promoted rather than negated. The output or response of the system increases the deviation from an ideal normal value. This amplification can lead to exponential growth, increasing oscillations, or even chaotic behavior.
- Loop Gain: Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect. The loop gain represents the extent to which the output of the system reinforces the input.
- Instability: Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there is typically exponential growth or divergence from equilibrium. This can lead to extreme values that may damage or destroy the system.
- Control and Limitation: Positive feedback can be controlled or limited in various ways. Signals in the system can be filtered, damped, or limited to prevent excessive amplification. Additionally, negative feedback can be introduced to counteract the positive feedback and restore stability.
- Examples: Positive feedback systems can be found in various fields. In biology, platelet clotting and the release of chemicals that speed up the process demonstrate positive feedback. In electronics, positive feedback is used to force voltages into ‘0’ and ‘1’ states. Positive feedback can also be observed in economic systems, mechanical design, and chemical reactions.
Amplification
In a positive feedback system, the original stimulus is amplified rather than negated. The output or response of the system increases the deviation from an ideal normal value. This amplification can lead to exponential growth, increasing oscillations, or even chaotic behavior.
Loop Gain
Mathematically, positive feedback is defined as a positive loop gain around a closed loop of cause and effect. The loop gain represents the extent to which the output of the system reinforces the input. A positive loop gain indicates that the output amplifies the input, leading to positive feedback.
Instability
Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there is typically exponential growth or divergence from equilibrium. This can lead to extreme values that may damage or destroy the system.
Control and Limitation
Positive feedback can be controlled or limited in various ways. Signals in the system can be filtered, damped, or limited to prevent excessive amplification. Additionally, negative feedback can be introduced to counteract the positive feedback and restore stability.
Examples
Positive feedback systems can be found in various fields. In biology, platelet clotting and the release of chemicals that speed up the process demonstrate positive feedback. In electronics, positive feedback is used to force voltages into ‘0’ and ‘1’ states. Positive feedback can also be observed in economic systems, mechanical design, and chemical reactions.
Conclusion
Positive feedback systems are characterized by amplification, instability, and the need for control. They can be found in various fields and play a role in diverse phenomena, from biological processes to electronic circuits. Understanding positive feedback is crucial in analyzing system behavior, preventing instability, and designing effective control mechanisms.
References
- https://www.cerritos.edu/rpcasas/positive-and-negative-feedback.htm
- https://en.wikipedia.org/wiki/Positive_feedback
- https://bio.libretexts.org/Bookshelves/Human_Biology/Human_Biology_(Wakim_and_Grewal)/10%3A_Introduction_to_the_Human_Body/10.7%3A_Homeostasis_and_Feedback
FAQs
What is a positive feedback system?
A positive feedback system is a process where the effects of a perturbation on a system include an increase in the magnitude of the perturbation. It amplifies the original stimulus, leading to exponential growth, increasing oscillations, or chaotic behavior.
How is positive feedback different from negative feedback?
In positive feedback, the output or response of the system increases the deviation from an ideal normal value. In contrast, negative feedback reduces or counteracts the original stimulus, bringing the system back to equilibrium.
What is loop gain in a positive feedback system?
Loop gain is a mathematical representation of the extent to which the output of a positive feedback system reinforces the input. A positive loop gain indicates that the output amplifies the input, leading to positive feedback.
Why is positive feedback often associated with instability?
Positive feedback tends to cause system instability. When the loop gain is positive and above 1, there is typically exponential growth or divergence from equilibrium. This can lead to extreme values that may damage or destroy the system.
How can positive feedback be controlled or limited?
Positive feedback can be controlled or limited in various ways. Signals in the system can be filtered, damped, or limited to prevent excessive amplification. Additionally, negative feedback can be introduced to counteract the positive feedback and restore stability.
Can you give some examples of positive feedback systems?
Positive feedback systems can be found in various fields. In biology, platelet clotting and the release of chemicals that speed up the process demonstrate positive feedback. In electronics, positive feedback is used to force voltages into ‘0’ and ‘1’ states. Positive feedback can also be observed in economic systems, mechanical design, and chemical reactions.
What are the potential benefits of positive feedback systems?
Positive feedback systems can be beneficial in certain situations. For instance, in biological systems, positive feedback can accelerate processes such as blood clotting and immune responses. In electronics, positive feedback can be used to create oscillators and amplifiers.
What are the potential risks of positive feedback systems?
Positive feedback systems can also pose risks. If not properly controlled, positive feedback can lead to instability, runaway growth, and even catastrophic failure. Examples include runaway nuclear reactions, population explosions, and financial market bubbles.