What kind of feedback is there? Why is feedback needed? See what “Feedback” is in other dictionaries

Feedback

management, cybernetic term, meaning information about the state of the control object and its reaction to the control action received by the control subject.

Dictionary of medical terms

Feedback

the impact of the results of the functioning of any system on the nature of its further functioning; one of the most important concepts of cybernetics, used in modeling the behavior of systems, including biological ones.

Encyclopedic Dictionary, 1998

Feedback

the impact of the results of the functioning of any system (object) on the nature of this functioning. If the influence of feedback enhances the results of functioning, then such feedback is called positive; if it weakens, it is negative. Positive feedback usually leads to unstable system operation; negative feedback stabilizes the functioning of the system and makes its operation stable. Used in automatic control systems, radio electronics devices, etc.; Feedback also operates in all living organisms.

Feedback

the reverse impact of the results of a process on its course or a controlled process on the governing body. O. s. characterizes regulation and management systems in wildlife, society and technology. There are positive and negative O. s. If the results of the process strengthen it, then O. s. is positive. When the results of a process weaken its effect, then negative O. s. occurs. Negative O. s. stabilizes the flow of processes. Positive O. s., on the contrary, usually leads to accelerated development of processes and oscillatory processes. In complex systems (for example, social, biological) determination of the types of O. s. difficult and sometimes impossible. O. s. They are also classified according to the nature of the bodies and media through which they are carried out: mechanical (for example, negative oxygen flow, carried out by a Watt centrifugal regulator in a steam engine); optical (for example, positive feedback, carried out by an optical resonator in a laser); electric, etc. Sometimes O. s. in complex systems it is considered as the transmission of information about the progress of a process, on the basis of which one or another control action is developed. In this case, O. s. called information. Concept of O. s. as a form of interaction plays an important role in the analysis of the functioning and development of complex control systems in living nature and society, in revealing the structure of the material unity of the world.

L. I. Freidin.

Feedback in automatic regulation and control systems, communication in the direction from the output to the input of the considered section of the main chain of influences (information transfer). This section can be either a controlled object or any link of an automatic system (or a set of links). The main chain of influences is a conditionally distinguished chain of signals passing from the input to the output of the automatic system. O. s. forms a path for the transmission of influences in addition to the main chain of influences or any part of it.

Thanks to O. s. the results of the functioning of automatic systems affect the input of the same system or, accordingly, its part, influence the nature of their functioning and the mathematical description of movement. Such systems with a closed chain of influences ≈ closed control systems ≈ are characterized by the fact that their input are both external and control influences, that is, coming from the controlled object to the control device.

Circuit (channel) O.S. may contain one or more links that convert the output signal of the main chain of influences according to a given algorithm. Example of a circuit O. s. ≈ a control device (for example, an automatic regulator) that receives the output (real) impact of the controlled object as an input value and compares it with the prescribed (in accordance with the operating algorithm) value. As a result of this comparison, the effect of the control device on the controlled object is formed (see Automatic regulation). Thus, the control object is covered by the O.S. circuit. in the form of a control device, the influence circuit is closed; such O. s. usually called the main one.

O. s. is a fundamental concept of cybernetics, especially control theory and information theory; O. s. allows you to monitor and take into account the actual state of the controlled system (i.e., ultimately, the results of the control system) and make appropriate adjustments to its control algorithm. In technical systems, control information about the operation of the controlled object is received through the O.S. circuit. to the operator or automatic control device.

Negative O. s. widely used in closed-loop automatic systems to increase stability (stabilization), improve transient processes, reduce sensitivity, etc. (sensitivity is understood as the ratio of an infinitesimal change in the output effect to the infinitesimal input effect that caused it). Positive O. s. enhances the output effect of a link (or system), leads to an increase in sensitivity and, as a rule, to a decrease in stability (often to undamped and divergent oscillations), deterioration of transient processes and dynamic properties, etc.

According to the type of transformation of the impact in the O. s. chain. There are rigid (static), differentiating (flexible, elastic) and integrating systems. Hard O. s. contains only proportional elements and its output effect is proportional to the input (both in statics and dynamics ≈ in a certain range of oscillation frequencies). Differentiating connections contain differentiating links (simple, isodromic) and can be astatic (disappearing over time) or with staticism. Connections without staticism appear only in dynamics, since their mathematical model does not involve the input effect, but only its derivatives, which tend to zero with the end of transient processes. In the composition of the integrating O. s. includes an integrating link that accumulates incoming influences over time.

For systems with OS. The following patterns are true. Proportional link when covering O. s. remains proportional with a new transmission coefficient, increased (against the original) for positive and decreased for negative O. s. A static link of the first order when covered by a rigid negative O. system. remains static of the first order; the time constant and the transmission coefficient change. Integrating link when covered by a rigid negative O. system. turns into static, and when covering isodromic O. with. begins to respond to the derivative (with respect to time) of the input influence. Static link of the first order when covering an isodromic O. with. also reacts to the derivative (with respect to time) of the input influence. When the proportional link of the integrating negative O. is covered. the result is an inertial-differentiating link. If, in this case, the original proportional link has a very large transmission coefficient (compared to the transmission coefficient of an isodromic O. system), then the resulting link approaches the differentiating one in its characteristics.

Lit.: Hammond P.H., Feedback Theory and Its Applications, trans. from English, M., 1961; Wiener N., Cybernetics, trans. from English, M., 1958; him, Cybernetics and Society, trans. from English, M., 1958; Theory of automatic control, part 1≈2, M., 1968≈72; Fundamentals of automatic control, 3rd ed., M., 1974.

M. M. Maisel.

Feedback in radio-electronic devices, the effect of a signal from the output of a device on its input. The electrical circuit through which the signal from the output of the device is supplied to the input is called the O.S. circuit. Most often, the device can be represented as an equivalent electrical circuit that has two (input and output) pairs of terminals, and can be characterized by the so-called. transfer function, or transfer function, defined by the ratio of the voltage or current at the output pair of terminals to the voltage or current at the input pair of terminals. Fc device transfer function with O.S. can be determined from the formula:

where F0 ≈ device transfer function without O.S.; b ≈ chain function O.s.; bF0 ≈ loop gain; 1 ≈ bF0 ≈ depth of O. s.

Classification of O. s. O. s. classified mainly by the type of transmission function of the O. s chain. and the relationship between the transmission functions of the O. s. chain. and the device itself, according to the nature of the O. s. circuit, according to the method of connecting the O. s. circuit. to the input and output of the device.

A distinction is made between linear and nonlinear O. s. depending on whether the transmission function of the circuit is linear or nonlinear. If bF0 ≈ real number and > 0, O.S. is positive; if bF0 ≈ real number and< 0, О. с. является отрицательной. При гармоническом входном колебании характер и глубина О. с. могут оказаться различными при разных частотах этого колебания. Такую О. с. называют частотно-зависимой. Она может быть положительной при одной частоте, когда фазы колебаний, которые подаются на вход устройства с выхода цепи О. с. и извне, совпадают (разность фаз Dj = 0╟), и отрицательной при др. частоте, когда они противоположны. При частоте, на которой Dj не равна 0╟ или 180╟, функция передачи цепи О. с. представляет собой комплексное число ; такая О. с. называют комплексной. При Dj, равной 90╟, О. с. называют иногда (чисто) реактивной. Если цепь комплексной О. с. содержит линию задержки, т. е. если Dj приблизительно пропорциональна частоте колебаний, О. с. называется запаздывающей.

According to the method of connecting O. s. circuits. To the input and output of the device, a distinction is made between serial and parallel O.S., if the output of the O.S. circuit. connected in series ( rice. 1, a, b) or parallel ( rice. 1, b, d) signal source, and mixed (combined) at the input, if the connection of the circuits is O.S. to the signal source serial-parallel. There are also O. s. by voltage and current, if the voltage or current is at the input of the circuit O. s. proportional to the voltage across the load resistance ( rice. 1, b, d) or the current in it ( rice. 1, a, c), and O. s. mixed (combined) at the output, if the connection of the circuits is O. s. to the load (output) resistance in series-parallel. OS, in which only noise and signal distortion occurring in the device are transmitted from the output to the input of the device, called. balanced.

Properties and applications of feedback. In a device with positive O. s. with a loop gain ≥ 1, self-oscillations can occur, which is used in various types of electrical oscillation generators. Positive O. s. with bF0< 1 применяют для усиления некоторых свойств устройства, например для увеличения селективности и чувствительности радиоприёмника при регенеративном приёме. Важнейшим свойством отрицательной О. с. является то, что она приближает функцию передачи устройства к функции, обратной функции передачи цепи О. с., и тем сильнее, чем больше глубина О. с. Поэтому её применяют главным образом для стабилизации параметров устройства (например, коэффициент усиления усилителя электрических колебаний) и уменьшения возникающих в нём нелинейных искажений (в 1 ≈ bF0 раз). Кроме функции передачи, О. с. изменяет входную и выходную реакции устройства с О. с. Отрицательная параллельная (последовательная) О. с. по напряжению (току) уменьшает (увеличивает) соответственно входное и выходное сопротивление устройства с О. с. Положительная О. с. ведёт себя противоположным образом. Комплексную частотно-зависимую О. с. применяют для создания т. н. активных электрических фильтров. Она также позволяет реализовать в электрических и радиотехнических устройствах элементы электрических цепей, не существующие в виде физических приборов, например элементы с отрицательной ёмкостью и с отрицательной индуктивностью, гиратор (преобразователь полного сопротивления, например ёмкостного в индуктивное) на любую рабочую частоту и элементы с электрически управляемыми параметрами (например, в виде реактивной лампы). Иногда такая О. с. используется для нейтрализации нежелательной внутренней О. с. в электронных приборах.

Several O. circuit circuits are often used simultaneously in one device. of various nature. An example is a tube amplifier ( rice. 2) with a complex frequency-dependent parallel O.S. by voltage, realized by mutual inductance (the so-called transformer O.S.), and negative series O.S. by current carried by a resistor. At a frequency equal to the resonant frequency of the oscillatory circuit, the transformer O. s. becomes positive. If its loop gain< 1 (с учётом действия отрицательной О. с), то всё устройство работает как регенеративный усилитель, в котором отрицательная О. с. стабилизирует глубину положит. О. с. и тем самым стабилизирует коэффициент усиления и полосу пропускания усилителя. Если же петлевое усиление ≥ 1, то устройство работает как генератор электрических колебаний, в котором отрицательная О. с. ограничивает ток через электронную лампу и улучшает форму колебаний на выходе, приближая её к синусоидальной.

Lit.: Braude G.V., Correction of television and pulse signals, Sat. Art., M., 1967; Tsykin G.S., Amplifier devices, 4th ed., M., 1971.

L. I. Freidin.

Feedback in biology. The existence of regulatory systems with O. s. can be traced at all levels of organization of living things - from molecular to population and biocenotic. The contribution of this mechanism is especially significant to the automatic maintenance of the constancy of the internal environments of the body - homeostasis, to the activity of the genetic apparatus, endocrine and nervous systems.

Ideas about regulation according to the principle of O. s. appeared in biology a long time ago. Already the first hypothesis about reflex reactions (R. Descartes, 17th century, J. Prochaska, 18th century) contained the premises of this principle. In a more clear form, these ideas were developed in the works of C. Bell, I. M. Sechenov and I. P. Pavlov, and later in the 30-40s. 20th century N.A. Bernstein and P.K. Anokhin. In the form that is most complete and closest to its modern understanding, the principle of O. s. (negative) ≈ as a general principle for all living systems ≈ was formulated by the Russian physiologist N. A. Belov (1912≈24) under the name “parallel-cross interaction” and experimentally studied on endocrine organs by M. M. Zavadovsky, who called it “plus ≈ minus interaction.” Belov showed that negative O. s. ≈ a general principle that ensures a tendency towards equilibrium in any (not only living) systems, but, like Zavadovsky, he believed that the existence of positive organic systems is impossible in living systems. Soviet scientist A. A. Malinovsky demonstrated the presence of all types of oxygen in living systems. and the differences in their adaptive significance were formulated (1945≈60). Abroad O. s. in biology began to be widely studied after the appearance of N. Wiener’s book “Cybernetics” in 1948. In the USSR in the 50-60s. 20th century I. I. Shmalhausen successfully applied the concept of O. s. in population genetics.

In living systems one should distinguish between O. s. types of mutual stimulation (positive OS) or suppression in response to stimulation (negative OS), amenable to at least an approximate quantitative assessment, and qualitatively complex OS, when, for example in ontogenesis, one organ promotes the differentiation of another , and the latter, at a new stage, determines the qualitative development of the first. General principles of O. s. formulated mainly for relations of the first type. Negative O. s. ensures that the system is maintained in stable equilibrium, because an increase in the impact of the governing body on the object (regulated body, system, process) causes the opposite effect of the object on the governing body. Physiological meaning of negative O. s. lies in the fact that an increase in the controlled variable (for example, the activity of an organ) above a certain limit causes a downward effect on the part of the subsystem associated with it; a sharp decrease in the controlled value causes the opposite effect. With a positive O. s. information about an increase in the controlled value causes a reaction in the subsystem associated with it, ensuring a further increase in this value. In highly organized animals, the activity of the central nervous system normally always includes, as a necessary condition, the presence of O. s. Thus, any action of an animal, for example, chasing prey, is accompanied by impulses coming from the central nervous system to the muscles (running, grasping prey), and feedback signals from the senses (vision, proprioceptors, etc.), allowing the results of efforts to be taken into account and corrected due to the course of events.

══ Self-regulation of vital processes is also due to O. s. Thus, a rise in blood pressure above normal is perceived by special receptors (for example, baroreceptors of the carotid sinus), which signal this to the vasomotor centers of the nervous system. This results in centrifugal impulses leading to a decrease in pressure (see Blood circulation). Such a process is an example of a negative negative reaction, most often observed in stable living systems. Most regulatory systems of animal and plant organisms work according to this principle. Positive O. s. predominate during embryonic development.

Many processes in ecology, for example, the regulation of population dynamics, are also based on positive and negative oxygen. Thus, a special case of negative O. s. represents the predator ≈ prey system considered by the Italian mathematician V. Volterra. An increase in the number of victims contributes to the increased reproduction of predators, and an increase in the number of predators, on the contrary, leads to a decrease in the number of victims. Although balance is maintained in nature in this way, due to the delay in the reproduction of animals, it takes the form of waves of life - wide fluctuations in the number of animals around the average level.

At the molecular level, according to the principle of O. s. a huge number of enzymatic reactions occurring simultaneously in a living cell are regulated. Coordination of this complex interconnected system is carried out by changing the activity of enzymes (negative enzyme activity is carried out by inhibitors, positive activity by stimulants) or the rate of their synthesis (operon activity is carried out by effectors; see Operon).

Combinations of positive and negative O. s. cause an alternative change in physiological states (for example, sleep ≈ wakefulness). Studying the development curve of pathological processes of a non-infectious nature (trophic ulcers, hypertension, manic-depressive psychosis, epilepsy, etc.) allows, based on the result, to determine the most likely type of OS underlying the disease and to limit the study of its etiology and pathogenesis by mechanisms of a certain category. Living objects, as the most advanced self-regulating systems, are rich in various types of oxygen; the study of the latter is very productive for studying biological phenomena and establishing their specificity.

Lit.: Malinovsky A. A., Types of control biological systems and their adaptive significance, in the collection: Problems of Cybernetics, ╧ 4, M., 1961, p. 151≈181; Regulatory mechanisms of the cell, trans. from English, M., 1964; Petrushenko L.A., The principle of feedback, M., 1967: Wiener N., Cybernetics or control and communication in animals and machines, trans. from English, M., 1968; Shmalgauzen I.I., Cybernetic issues of biology, Novosibirsk, 1968.

A. A. Malinovsky.

Wikipedia

Feedback

Feedback- in a broad sense means feedback, response, response to any action or event:

• Feedback
  • Acoustic feedback
• Feedback
• Feedback
• Feedback

• Feedback

Feedback (cybernetics)

Feedback in cybernetics, this is the presence of circuit cycles in the unchangeable part of the machine, and conditional instructions in its changeable part. Feedback distinguishes a special class of automata that participate in a certain type of scientific experiments or are used in practice.

Feedback (technique)

Feedback in technology, it is a process that leads to the fact that the result of the functioning of a system affects the parameters on which the functioning of this system depends. In other words, a signal is applied to the input of the system that is proportional to its output signal (or, in general, is a function of this signal). This is often done deliberately to influence the dynamics of the system.

There are positive and negative feedback. Negative feedback changes the input signal in such a way as to counteract the change in the output signal. This makes the system more resistant to random changes in parameters. Positive feedback, on the contrary, enhances the change in the output signal. Systems with strong positive feedback tend to be unstable; undamped oscillations may occur in them, that is, the system becomes a generator.

Feedback (society)

Feedback in society, as a connection between the managed and the managers for the transfer of information from the managed to the manager, it serves as an important element of the political system as control “from below” over the subject of power; is considered as a communication network that produces actions in response to input of information and allows you to incorporate the results of political decisions into your subsequent behavior; If the goals of the political system are realized, then target feedback begins to operate, giving impetus to changing the goals of the system.

Feedback mechanisms play a system-forming role in the process of communication between government and society; the process of institutionalization of feedback serves as an indicator of the level of political and democratic development of society. In modern communication theory, feedback is recognized as a necessary process that ensures the functioning, adaptation and development of any highly organized system (Miller, 2003 ;Harris, 2002).

According to researchers (Easton, David), interactions between the political system and society as a whole, defined as “exchanges” and “transactions,” are realized in the form of “input-output” relationships, where input is demands and support, and output is decisions and actions, “input-output” relationships form a feedback loop that transfers information about the effectiveness of “outputs”: the reactions of the political system to external and internal influences, which is of key importance for assessing the effectiveness of the political system as a whole and makes it possible to model and predict the consequences of political decisions.

Feedback- this is a response to a speech utterance: an answer to a question, agreement or disagreement, a new speech, etc. Feedback can take the form of action; after listening to the speaker, people act on his recommendations.

Feedback is the verbal and nonverbal messages a person intentionally or unintentionally sends in response to another person's message.

The listener is able to influence the speech behavior of the speaker precisely because he is nearby and his reaction is obvious. This reaction is nothing more than (in terms of information theory) a manifestation of feedback.

In interpersonal communication, we constantly provide each other with feedback, whether we want it or not. Everything we do or fail to do towards or in interaction with others can be considered feedback. Let's say a young man wrote several dozen letters to a girl and did not receive an answer to one - the feedback in this case is the lack of action. We laugh at a joke told when we really find it funny or when we want to please the teller - these are examples of spontaneous and deliberate feedback. Love expressed by a glance or a poetic message are examples of nonverbal and verbal feedback. If our words or actions cause an undesirable reaction in someone and we rush to accompany them with the phrase: “You misunderstood me...” or “That’s not what I meant at all” - this is how we try to control the feedback.

A person’s actions, in which her ability to hear turns out to be, precisely because of their “reactive” (that is, reacting to a stimulus) nature, provide the very possibility of feedback, and all the factors discussed above, improving the ability or preventing it, directly affect the content of the feedback. "connections.

Among the types of feedback are: evaluative and non-evaluative reverse. Evaluative Feedback - communicating your opinion, your attitude to what is being discussed.

A group of American researchers led by A. Jacobs investigated a phenomenon called the “jump in probability.” Its essence lies in the fact that positive feedback is always assessed as more reliable than negative feedback. With regard to the optimal sequence of feedback delivery, a number of experimental data suggest that negative feedback is rated as more credible and desirable when given after positive feedback rather than before it.

The mentioned group of researchers conducts experiments in accordance with a “long-term” program, studying the dependence of feedback acceptance on three variables: 1) the sign of feedback ("+" or "-") 2) the sequence of its presentation - first "+", then "- ", and vice versa; 3) form of feedback: a) behavioral (“I think you’re acting too bossy”), b) emotional (“I like you,” “I’m angry at you”), c) emotional behavioral (“You’re acting bossy.” , and that makes me angry.").

One of the ways to increase the reliability of feedback, discovered during an experiment called the “amplifying effect.” Its essence is that the emotional "additive" to the behavioral basis increases the likelihood of feedback compared to purely behavioral feedback, if both are positive. And the emotional addition itself reduces the likelihood of feedback if it is negative. In other words, “reinforcing” a positive behavioral observation (“You're attentive”) with a positive emotional response (“I like you”) increases the likelihood of a behavioral observation, while pairing a negative behavioral observation (“You're distracted”) with a negative emotional response ("I don't like you") reduces the credibility of a behavioral comment: the comment may be perceived as biased and caused by a negative attitude. A. Jacob believes that the use of the "reinforcement effect" is a powerful lever for changing the likelihood of feedback.

Evaluations can be positive (“you’re doing well”) or negative (“what nonsense are you talking about”). Positive evaluative feedback serves the function of supporting the “I-concept” of our partner and the interpersonal relationships that have developed with him.

Negative evaluative feedback performs a corrective function aimed at eliminating undesirable behavior, changing or modifying our relationships.

The structure of evaluative feedback involves the use of phrases that indicate that we are talking about a person’s own opinion: “it seems to me,” “I think,” “in my opinion.” If such expressions are absent, and the assessment is expressed quite definitely and openly, then the statements acquire a static character, are often perceived as rudeness or impoliteness and cause psychological defense in the interlocutor. Therefore, relationships become strained or even collapse. Let's compare the statements:

“It seems to me that this is not so” and “How stupid!”

Non-judgmental feedback - type of feedback does not contain our attitude to the issue under discussion. We use it when we want to learn more about a person's feelings or help her formulate an opinion on a specific issue, without directly interfering with the actions of the interlocutor.

This goal is achieved through techniques such as clarification, paraphrasing, clarification, and reflection of feelings (or empathy). Such procedures formed the basis for the identification of listening styles that we discussed earlier.

So, feedback is a necessary component of effective communication.

In the case of an amplifier operating with its final, that is, already amplified signal, a direct effect on its output level appears. That is, the so-called feedback appears. In fact, for ease of understanding, such a connection can be compared to a train that moves along a roundabout and all the cars are attached one after another without breaking.
So, this feedback is positive when the train accelerates, and negative when it slows down. Of course, these are all conventional concepts, but to make everything clear and reliable, let’s look at examples of PIC and OOS, not using the example of a train, but in electronics, where they are found.

What is Positive Feedback POS

Positive feedback is a type in which a change in the output signal of the system leads to such a change in the input signal, which contributes to a further deviation of the output signal from the original value, and in the case of negative feedback, the completely opposite process occurs.
Many of us have encountered an example of the feedback that occurs in a speaker set: when a speaker holds a microphone too close to the speakers, a high-pitched “howling” sound occurs, which is due to the audio amplifier picking up and amplifying its own noise. This phenomenon is an example of positive or regenerative feedback, since any sound entering the microphone is amplified and turned into an even louder sound from the loudspeaker and thus creates a feedback loop in which the vibration maintains itself, increasing more and more, resulting in noise arises with ever-increasing volume until the system enters a state of “saturation” and can no longer amplify the sound.
One might wonder what the possible benefits of feedback in amplifiers are, given such annoying manifestations as the "howling" sound of performance PA equipment. If we introduce positive or regenerative feedback into the amplifier circuit, then a tendency will be created to generate and maintain oscillations, the frequency of which is determined by the values ​​of the components that supply the feedback signal from the output to the input. This is one way to make a generator, a circuit for receiving alternating current from a direct current source. Oscillators are extremely useful circuits, and so feedback can have some practical applications.

What is Negative Feedback OOS

Negative feedback, on the other hand, has a “softening” effect on the amplifier: as the amplitude of the output signal increases, the feedback signal counteracts the change in the output signal. While positive feedback makes the system less stable, negative feedback does the opposite: it only makes the system more stable.
An amplifier driven by negative feedback is not only more stable, but it also distorts the input signal less and can generally amplify over a wider frequency range. The trade-off for these benefits (there must be some downsides to negative feedback, right?) is a reduction in gain. If part of the amplifier's output signal "feeds back" to the input, and counteracts any changes in the output signal, then a larger amplitude input signal is required to provide the same amplitude at the output. This is what causes the reduced gain in the presence of negative feedback. In any case, the benefits of stability, reduced distortion and wider bandwidth are worth the sacrifice of some gain.
Let's look at a simple amplifier circuit and determine how we could introduce negative feedback into it (see figure below).

Common emitter amplifier without feedback

The diagram shows a common emitter amplifier in which the bias resistor chain is formed by resistors R1 and R2. The capacitor connects Vin to the amplifier in such a way that the signal source does not have a DC voltage supplied by the voltage divider R1/R2. Resistor R3 serves to control the voltage gain. At maximum voltage gain, this resistor can be omitted, but since similar base resistors are often used in common-emitter amplifier circuits, it is shown in the figure.
Like all common emitter amplifiers, the amplifier shown inverts the amplified incoming signal. In other words, an increasing voltage of the input signal leads to a drop in the output voltage and vice versa. The figure below shows the waveforms on an oscilloscope.

Open-loop common emitter amplifier and original waveforms for comparison

Since the output signal is a mirror image copy of the input signal, any connection between the output (collector) and the input (base) of the transistor (as shown in the figure below) will create negative feedback.

Negative feedback, collector feedback weakens the output signal

Resistors R1, R2, R3 and Rrev.sv. together operate such that the voltage at the base of the transistor (relative to ground) is the average of the input voltage and the feedback voltage, resulting in a lower amplitude signal being sent to the transistor. So the amplifier circuit in the figure above will have reduced voltage gain, but better linearity (less distortion) and wider bandwidth

To summarize about positive and negative feedback (POC and NFC)

Feedback is the supply of the amplifier's output signal to its input.
Positive or regenerative feedback leads to such a change in the input signal that it causes the output signal to deviate from the original value and oscillations (alternating current) occur in the system. The frequency of these oscillations is largely determined by the selection of feedback circuit components.
Negative feedback promotes stable operation of the amplifier so that the change in output signal is less for a given input signal than if there was no feedback. This leads to a decrease in gain, but also provides certain advantages: reduced distortion and increased bandwidth (operating frequency range).
Negative feedback can be introduced into a common emitter circuit by connecting the collector to the base, or by connecting a resistor between the emitter and ground.
An emitter-to-ground feedback resistor is commonly used in common emitter circuits as a preventive measure against temperature-induced distortion.
Negative feedback also has the advantage that the voltage gain becomes more dependent on the resistor values ​​and less dependent on the characteristics of the transistors themselves.
Common collector amplifiers have deeper negative feedback due to the presence of a load resistor between the emitter and ground. This feedback provides extremely stable gain, as well as protection against distortion caused by rising transistor temperatures.
The gain of a common emitter amplifier can be restored without compromising distortion immunity by connecting a shunt capacitor in parallel with the emitter "feedback resistor".
If the voltage gain is arbitrarily high (10,000 and above), and negative feedback is used to reduce the gain to a reasonable level, then the gain will be approximately equal to Rrev.st. / Rin.. In the presence of feedback, changes in the gain of the transistor? or other component parameters will not have much influence on the voltage gain, resulting in a stable amplifier of a simple design.

Feedback(feedback) - information that an employee receives about how the manager perceives and evaluates his actions.

Why feedback is needed:

1. With its help, the manager manages the activities of his subordinates, that is, he encourages the desired behavior and limits the unwanted. By praising an employee, he thereby confirms the correctness of his actions, compliance with the plan, and the ideas of the manager. If it is necessary to change the actions of a subordinate, the manager gives corrective feedback. This achieves the main thing - ensuring the effectiveness of the subordinate’s actions.
2. Feedback has a teaching function. It allows the employee to find out what is expected of him, what are the criteria for evaluating his work, and how much his actions correspond to the correct technology for performing the work.
3. It performs a motivating function. The manager praises, encourages the employee and recognizes his achievements, thereby creating motivation for further work. With the help of corrective feedback, the manager creates a desire to correct the situation.
4. Providing detailed feedback is a manifestation of attention to the employee on the part of the manager, which has a beneficial effect on the relationship between people working together.

Thus, feedback is the most important component of such management processes as control, mentoring, motivation, and has the most powerful potential as a tool of managerial influence. For this potential to be realized, the following conditions must be met. Feedback should be:

1. Specific. The manager should not generalize and make global conclusions like: "You're always late for work", better to say . In feedback it is necessary to operate with specific facts, and not general judgments.
2. About actions, not about personality. Acceptable statement "You're 15 minutes late today", but not "you are an undisciplined person". An action can be corrected, but a character cannot be corrected. Therefore, a person is ready to accept information about the action, but is not ready to agree that he is some kind of different person, and will defend himself and argue.
3. Timely. Feedback should be given immediately after the behavior you want to encourage or change. This is also called the “hot stove rule” (if you touch it, the burn occurs immediately, not later).
4. Developmental. One of the tasks of feedback is to develop the employee’s ability to self-analysis, independently highlight his successes and shortcomings, and correctly search for their causes. To do this, the manager uses open ones, helping the subordinate himself to formulate the correct conclusions about his work. Conclusions drawn independently are accepted and remembered much better than those said by another person.
5. Adapted. All people are different in their level of sensitivity to criticism and readiness for self-development. The manager needs to adapt his feedback to the level of understanding of his subordinates: do not give a lot of corrective information at once if the person is able to understand and implement only part of it.

There are several models for structuring feedback, the most commonly used are the following:

1. "Sandwich Rule" Feedback is provided according to the structure “Positive - Corrective - Positive”. Such a structure is necessary for those employees who may not be emotionally ready to accept the need to adjust their actions. To prevent the employee from taking a defensive position in communication with the manager, feedback begins and ends with positive aspects in his activities (achievements, successes, strengths).

...In one of the companies, the supervisor had a tough, impartial conversation with a sales representative about the unconvincing dynamics of fulfilling planned tasks. At the end of the conversation, suddenly remembering the “sandwich rule,” the supervisor lowered his voice and said: “Well, in general, you’re great, customers at retail outlets speak well of you. Go to work". To which the sales representative, leaving, plaintively remarked: “Uncle Fyodor, your sandwich is somehow wrong...”

1. The BOFF model (Behaviour – Outcome – Feelings – Future), in the Russian version of the BCBB (Behaviour – Result – Feelings – Future). First, the manager describes the employee's behavior and the result to which this behavior led. Further, he enhances the emotional impact by mentioning the feelings that he (or the employee’s colleagues, the employee himself, other persons) feel about this. The feedback ends with a description of the desired behavior that the employee must demonstrate in the future. The model is used if the manager has doubts that regular feedback will be effective for a given employee.
2. Model SOR (Standard – Observation – Result, Standard – Observation – Result). Designed to orient the employee to the correct technology of action. First, the manager reminds the employee of the existing actions in the company, then discusses with the employee his observations about his behavior, reaches the employee’s understanding of the results that his behavior can lead to, and achieves the employee’s willingness to comply in the future.

In addition to the ability to provide feedback, you also need to learn yourself and teach your subordinates to accept it correctly. To do this, it is important to follow several rules:

1. When receiving feedback, do not make excuses and avoid being defensive.
2. Ask questions for clarity, ask for examples of behavior, summarize the information received, and get confirmation that you understood it correctly.
3. Thank you for your feedback.
4. Make an action plan on what and how you can improve.

In the FMCG field, much attention has traditionally been paid to managers’ compliance with the rules for providing and receiving feedback, which can be enshrined in a number of other processes. For example, one of the functions of a meeting is summing up, i.e. providing feedback to the team, which should also be carried out taking into account the rules described above. This means that during the meeting he must operate with specific, relevant figures and facts (the rules of “specificity”, “timeliness”), start with the positive and achievements of the team (the “sandwich” rule), and focus on what needs to be improved today ( “adaptability” rule). At the same time, he should never “criticize” individual subordinates in the presence of others, that is, he must praise in public and criticize one by one.

the process of a person obtaining information about the results of his own speech and non-speech actions, in particular about how the interlocutor reacts to him. O. s. allows a person to regulate his behavior, constantly consider whether the set goals are being achieved during communication, and replace the methods of verbal interaction used with more effective ones. This may be a new speech act, which has its own motivation, its own stages of internal preparation, oral or written implementation, for example, a new remark in a dialogue; letter to the editor - response to an article, etc. The results of speech interaction can manifest themselves in changes in the nature of material and practical actions of a kinesic nature (in facial expressions, gestures, intonation, etc.), in speech actions. In this regard, three types of O. are distinguished: 1) operating room (serves as the basis for adjusting information interaction); 2) kinesic (used for the purposes of adequate speech perception); 3) speech (manifests in the form of self-evaluative judgments of the speaker, in his response speech actions). So, positive operating O. s. can manifest itself when the speaker sees that his interlocutor is writing down something from what he is saying and nods in agreement with him. Negative O. s. manifests itself in situations when the interlocutor is distracted and looks bored. Speech O. s. manifests itself in remarks and questions: That’s right! Correct!, which serve as confirmation that the interlocutor listens with attention and interest, correctly evaluates the information, and therefore no adjustments are required: Yes, I agree with you. The work should be stopped for two reasons... (a judgment that continues the interlocutor’s thought speaks of a positive speech O. s). Lit.: Wiener N. Cybernetics, or Control and Communication in Animals and Machines. - M., 1968; Genov F. Psychology of management. - M., 1982; Kasatkin S.F. Feedback in oral presentation. - M., 1984. OM. Kazartseva