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Basics of Feedback Systems
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Welcome everyone! Today, we will discuss feedback systems. So, what do we think a feedback system is?
Is it the process where output from a system is used as input?
Exactly! To reinforce this, remember the acronym 'OC' for Output Control. This means the output directly influences the input. Now, can anyone give me an example of this in real life?
Like a thermostat controlling the heating in a room?
Spot on! That's a perfect example of a feedback system. Letβs move on to distinguishing between the two types of feedback systems.
Types of Feedback Systems
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We primarily have two types of feedback systems: negative and positive feedback. What do you think negative feedback does?
Doesn't it stabilize the system?
Correct! Negative feedback reduces discrepancies. On the other hand, what about positive feedback?
It reinforces changes, right?
Exactly! Remember the mnemonic 'Resound' for Positive Feedback: Reinforces changes. Let's move to how we derive the transfer characteristics.
Transfer Characteristic Derivation
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Now, letβs derive the transfer characteristic of a feedback system. Can anyone remind us of the formula we use?
Is it S = A(S - B2S)?
Yes! S represents the system output, whereas B2 represents the feedback factor. To remember the steps, think of the acronym 'FLO' for 'Find, Loop-back, Output'.
Okay, so we find the forward gain, loop it back through feedback and then get the output!
Precisely! And understanding this paves the way to grasp concepts like loop gain and desensitization factor.
Loop Gain and Desensitization Factor
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What would you say is the significance of the loop gain?
It reflects how often the feedback signal is multiplied before it affects the system.
Exactly! Loop gain affects stability. Additionally, consider the desensitization factor as it determines how changes affect the feedback system.
Oh, I see! So, a high desensitization factor means the circuit is less sensitive to variations?
Right again! As you study this, remember 'D-SS' for 'Desensitization - Stability Support'.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section elaborates on the basics and types of feedback systems, deriving their transfer characteristics and discussing the significance of configurations in analog circuit design. Students will learn about the positive and negative feedback characteristics as well as how to identify and analyze their impacts.
Detailed
Transfer Characteristics of Feedback System
This section dives into the fundamentals of feedback systems in analog electronic circuits. Feedback systems are crucial in amplifiers, where the basic configuration involves sampling an output signal to provide input back to the system. The section begins by explaining how feedback operates, identifying two primary types: negative (C9-feedback) and positive (C9-feedback).
Key Points Covered:
- Basic Interaction of Feedback Systems: The input signal (voltage or current) is augmented by an amplification factor (A). Feedback mechanisms not only enhance functionality but also stabilize the circuit.
- Configurations: Four configurations intrinsic to feedback systems are introduced, emphasizing their flexibility and application in various analog designs.
- Derivation of Transfer Characteristics: The section proceeds with an analysis on how to derive the transfer characteristic of the feedback system, leading to significant formulas like {S} = {A}(S - B2S).
- Loop Gain and Desensitization Factor: Two critical measures of system stability and performance: the loop gain and desensitization factor are also examined. Both these concepts provide insight into how feedback alters system sensitivity and gain.
- Assumptions: Multiple assumptions in defining the feedback systems, like unidirectionality of signals and ignoring loading effects, are tackled, ensuring practical applications are understood.
This foundational knowledge profoundly aids further studies in circuit design, providing a base for advanced concepts in electronics.
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Basic Model of Feedback System
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In fact, different amplifier configurations and those amplifiers are essentially linear circuit. So, we can say that at the input, we are applying input signal either it may be in the form of voltage or current. On the other hand at the output, we are observing the corresponding amplified version of the input signal and this A represents the amplification factor. So, this is I should say basic model of whatever the amplifier we have discussed. This input need not be single ended, it can be even differential and we know the signal it is propagating from left to right from the input port to the output port. Whenever you are talking about the feedback system, what we are trying to do, we are essentially sampling this signal and part of it we are taking back and we are given to the input.
Detailed Explanation
A feedback system involves amplifiers that take input signals (voltage or current) and produce amplified output. The amplification factor is denoted by 'A'. The feedback system works by sampling part of the output signal and feeding it back to the input to influence the overall amplification process. This feedback can either enhance or reduce the output based on the system's configuration.
Examples & Analogies
Consider a teacher giving feedback to a student during a presentation. If the teacher encourages the student ('positive feedback'), the student gains confidence and performs better. Conversely, if the teacher points out errors ('negative feedback'), the student may adjust their presentation to improve clarity.
Feedback System Components
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In this feedback system what are the basic modules we do have first of all we do have forward amplifier. So, this is called forward amplifier which is taking the signal from left to right and then we also have feedback path. So, we do have the feedback path here through which, we are taking the primary output and bringing the signal back to the input port of the amplifier. So, we do have the feedback path and its transfer function it is Ξ² for forward amplifier the transfer function it is A.
Detailed Explanation
In a feedback system, the primary components include the forward amplifier, which amplifies the input signal, and the feedback path, which returns a portion of the output signal to the input. The forward amplifier has a transfer function, represented as 'A', while the feedback path has a transfer function 'Ξ²'. These components interact to control the overall output based on feedback.
Examples & Analogies
Think of a thermostat in a room heating system. The thermostat senses the room temperature (feedback) and sends a signal to the heater (forward amplifier) to increase or decrease heat. The system balances itself through this feedback to maintain the desired temperature.
Types of Feedback Systems
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So, what we said is that, the basic types of feedback system it is, we make say it is βve feedback system or +ve feedback system.
Detailed Explanation
Feedback systems can be classified into two main types: negative feedback and positive feedback. In a negative feedback system, the feedback signal reduces the output signal, stabilizing the system. In contrast, a positive feedback system amplifies the original signal, potentially leading to runaway effects. Understanding these types is crucial for predicting system behavior.
Examples & Analogies
Consider a microphone near speakers. If the speakers amplify sound (positive feedback), it can create a loud screeching noise as the sound is continually amplified. However, if you were to adjust the volume down (negative feedback), it prevents the screeching and stabilizes the sound.
Negative Feedback Explained
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When we call it is βve feedback system? Suppose, in first of all it is having a feedback, whether we call it is +ve or βve. So, the signal it is looping around this path which is going through this forward amplifier and also it is going through the feedback path... If it negates the original change then the feedback system it is called βve feedback system.
Detailed Explanation
Negative feedback occurs when the feedback signal counteracts or negates the changes in the output. This creates a loop where the output tries to stabilize by opposing any increase or decrease in the signal. As a result, negative feedback enhances system stability and accuracy.
Examples & Analogies
Think of a car's cruise control system. If the car speed increases beyond the set limit, the system slows the car down to maintain that speed. Here, the feedback (current speed) opposes the change (excessive speed), thereby stabilizing the car's speed.
Positive Feedback Explained
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On the other hand in case if the; signal it is if the change if the created effect due to a change coming back through the feedback path, if it is aggravating the original change; that means, if it is in the same phase. Then we call the feedback system it is +ve feedback system.
Detailed Explanation
Positive feedback occurs when the feedback signal enhances or aggravates the output change. Instead of counteracting, it boosts the original effect, which can lead to rapid increases in output but can also destabilize the system if uncontrolled.
Examples & Analogies
Imagine a microphone picking up applause in a concert. As the audience claps, the sound is amplified, causing even more applause due to excitement (positive feedback). This amplifying effect continues until it potentially causes distortion or feedback noise in the system.
Transfer Characteristic Derivation
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So, the as I said that we may have different situation, but without loss of generality, let us consider that primary port, it is having + sign at the mixer terminal and the feedback signal terminal it is having β sign which means that this S = S β S.
Detailed Explanation
The transfer characteristic of a feedback system is derived by examining the signal flow through the system's components. By defining the input and output signals and analyzing the transfer functions, we can establish the overall transfer function of the feedback system, which reflects how the input is modified by the feedback.
Examples & Analogies
Think of it as creating a recipe (transfer function). The input (ingredients) combines and changes the outcome (dish). The way you adjust ingredients based on taste feedback creates a unique dish (output), illustrating how the transfer function modifies the input into a desired result.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Feedback Systems: Processes that modify input based on output.
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Negative Feedback: Acts to stabilize a system by countering changes.
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Positive Feedback: Amplifies the input signal, thus reinforcing changes.
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Transfer Characteristic: Mathematical relationship of input-output in feedback.
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Loop Gain: Total gain of the system considering feedback.
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Desensitization Factor: Change in system sensitivity due to feedback.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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In an audio amplifier, feedback reduces distortion and enhances stability by feeding part of the output back to the input.
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Thermostats use negative feedback to maintain temperature by turning heating/cooling on or off based on sensed temperature changes.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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Feedback systems twist and twirl, stabilizing signals as they swirl.
π Fascinating Stories
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Once a loudspeaker struggled to control sound; it found a feedback path to settle down.
π§ Other Memory Gems
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For types of feedback, remember 'NP' - Negative stabilizes, Positive amplifies!
π― Super Acronyms
Use 'FLD' for Feedback Loop Dynamics, covering the main concepts!
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Feedback System
Definition:
A process that uses the output of a system to influence its input to enhance stability and control.
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Term: Negative Feedback
Definition:
A type of feedback that reduces discrepancies and stabilizes the system by opposing changes.
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Term: Positive Feedback
Definition:
A type of feedback that enhances changes and reinforces the direction of the system's output.
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Term: Transfer Characteristic
Definition:
The relationship between the input and output of a system, typically expressed as a mathematical expression.
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Term: Loop Gain
Definition:
The gain of a feedback loop, measured as the product of the forward gain and feedback factor.
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Term: Desensitization Factor
Definition:
A factor that quantifies the change in system gain due to negative feedback.