What is negative feedback?

Although the term "negative feedback" is not known to everyone, every person faces every day the process behind it. There are a lot of examples. Moreover, interestingly, negative feedback is characteristic not only of living organisms, but also of many technical means. In part, only thanks to her progress exists in the form to which we are all accustomed.

The principle of feedback is studied in various branches of science. For example, in music, some rock artists such as Kurt Cobain, Link Ray and others have become especially famous for the ability to use feedback (feedback) . They study it in biology, mechanics, electrical engineering, radio electronics ... in fact, everywhere. Accordingly, it is easy to find many different answers to the question "what is negative feedback" in the global Network, but often the answers themselves generate new questions. All this despite the fact that the meaning of feedback is extremely simple.

What is negative feedback? Here are some life examples. Imagine a person walking on a slippery surface. Here he takes one step, then another, a third ... and then the foot begins to slide, the center of gravity of the body gradually (it just seems that instantly) shifts - there is a real danger of falling. At this point, certain muscle groups are contracting, trying in some way to compensate for the unstable state. This can be a backward deflection or, conversely, a few frequent steps forward with the body tilted. However, in this case, we described only external manifestations. The internal work mechanism is as follows:

• The leg becomes to the surface. At this point, signals are sent from her to the brain indicating strength (each without hesitation, will determine a soft or hard base), roughness, bias;
• In accordance with the received data, the position of the body and placement of the foot are corrected;
• But my leg began to slide. The threat of sustainability. The more intense the slip, the more actively the search and implementation of the optimal method that can prevent a fall occur.

Positive feedback is used by the skier, who even tilts the casing, increasing the speed of sliding. In turn, a negative relationship counteracts the cause that gave rise to changes in the system.

By the way, many fans of computer games know the rudders with feedback. This is it! The stronger the player turns the steering wheel to the side, the greater the resistance from the internal electric motor he experiences. In this example, there is a current feedback.

Schematically it looks like this: input - system - output. With any changes to the input data, there is a corresponding change in the output. The latter, while doing so, affect the system to return it to its original stable state.

The feedback in the amplifiers allows solving several problems at once: to ensure the stability of the gain, regardless of the input signal, to make the entire system work completely automatic (feedback adjustment is performed only at the initial stage). However, negative feedback in electronics is not always so simple. The peculiarity is that the feedback signal arriving at the system must have time to activate the compensating mechanisms earlier than the input data will be changed again. In other words, the speed of the feedback should exceed the rate of change in the input signal. Therefore, for circuits based on ultrahigh frequencies, a number of difficulties arise. One solution is to synchronize the frequencies of input data and feedback.