90.1.3 - Types of Feedback Systems
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Introduction to Feedback Systems
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Welcome everyone! Today, we're diving into feedback systems within electronic circuits. To start, can anyone explain what feedback means in this context?
Isn't feedback when the output is fed back to the input to influence the signal?
Exactly, Student_1! Feedback can help stabilize or enhance a circuit's performance. There are two main types: negative feedback and positive feedback. Who can tell me the difference?
Negative feedback reduces the output signal, while positive feedback increases it?
Correct! Think of negative feedback as a brake, and positive feedback as an accelerator. Let’s remember that with the acronym **PEAC** - Positive feedback Enhances, Negative feedback Attenuates Change.
Could you explain how these types affect circuit stability?
I’d be glad to! Negative feedback leads to a stabilizing effect which can linearize the output. In contrast, positive feedback can lead to instability but may be beneficial in oscillators. Let's summarize - we explored feedback meaning, types, and their effects on circuit behavior.
Understanding Negative Feedback Systems
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Now, let's dive deeper into negative feedback systems. Who can describe how they function in simple language?
I think it regulates the output by reducing deviations from a set point, right?
Absolutely! Negative feedback can help maintain a stable output by counteracting changes. Why is this useful in amplifiers or other circuits?
It makes the amplifier more predictable and less sensitive to noise!
Exactly, Student_1! Repeat after me: **Stability comes from Negative feedback**. Now, consider an example: How might we implement a negative feedback loop in a practical amplifier circuit?
By connecting a portion of the output back to the input, but inverted, right?
Correct! This reduces distortion and enhances linearity. Let's summarize the advantages of negative feedback: stability, reduced distortion, and improved bandwidth!
Exploring Positive Feedback Systems
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Now, let’s contrast this with positive feedback. What are the characteristics of positive feedback systems?
I think they amplify the effects of changes, potentially leading to runaway effects?
Spot on! Positive feedback can lead to instability but is particularly useful in circuits like oscillators. Can anyone provide a real-world example?
How about in a microphone feedback loop?
Great example! If the microphone picks up its amplified sound, it keeps increasing, leading to that screeching sound. Let's remember, **Positive feedback Propels changes.**
And in a regenerative circuit, right?
Exactly right! These principles are crucial for designing oscillators and timers. We’ve now covered both feedback types thoroughly!
Introduction & Overview
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Quick Overview
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In this section, we explore the basic theory of feedback systems, detailing how signals are amplified in electronic circuits. We classify feedback systems into negative and positive categories, providing an understanding of how feedback affects signal integrity and system behavior.
Detailed
Types of Feedback Systems
The section discusses the concept of feedback in analog electronic circuits, focusing on how input signals can be modified through amplification. The feedback system comprises a forward amplifier, a feedback path for signal sampling, and a mixing mechanism that alters the input signal based on feedback. Feedback systems are classified into two primary types:
1. Negative Feedback Systems
In a negative feedback system, feedback diminishes the original signal change. When a change occurs in the system and is fed back negatively, it counters the initial effect, stabilizing the circuit's behavior.
2. Positive Feedback Systems
Conversely, a positive feedback system amplifies the original signal change. When the feedback signal reinforces the change, it leads to increased response in the system.
The section progresses to derive the transfer characteristics of feedback systems, highlighting crucial concepts like forward amplification (A), feedback factor (β), and the overall system gain. The importance of understanding feedback type is emphasized for the effective design and implementation of analog circuits.
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Overview of Feedback Systems
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Chapter Content
In this feedback system, the basic types of feedback system it is, we make say it is ‒ve feedback system or +ve feedback system.
Detailed Explanation
This segment introduces the basic types of feedback systems, which are categorized as negative (‒ve) feedback systems and positive (+ve) feedback systems. Feedback in a system involves returning a portion of the output back to the input to modify the system's operation.
Examples & Analogies
Think of a thermostat in your house. When the temperature rises above a set point, the thermostat sends a signal to the air conditioner to cool it down - this is an example of negative feedback. Conversely, a positive feedback scenario could be likened to a microphone too close to a speaker, creating a loud echo that amplifies itself.
Negative Feedback Systems
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When we call it a ‒ve feedback system? Suppose, in first of all it is having a feedback, whether we call it is +ve or ‒ve. 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 and of course, we do have sampler and mixer.
Detailed Explanation
In negative feedback systems, the feedback signal opposes the input signal, reducing the overall gain and stabilizing the system. It helps in minimizing errors and improving bandwidth. For instance, if the output is increasing, the negative feedback reduces the input to bring it back to desired levels.
Examples & Analogies
Imagine driving a car. If you realize you are going too fast (the output is high), you would step on the brake (the negative feedback) to slow down to a safe speed. The feedback in this sense helps to maintain control and stability.
Positive Feedback Systems
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In case 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 systems work in a way that enhances the effect of the input signal. Instead of reducing the output, these feedback systems amplify it, pushing the output further in the same direction, which can lead to exponential growth or oscillations in the system. For instance, if the output encourages further increases in the output itself, it leads to a reinforcing loop.
Examples & Analogies
Think of a snowball rolling down a hill. As it picks up speed, it also picks up snow (output) making it grow larger and roll faster (aggravating the original change). This is similar to positive feedback where an initial change propagates and magnifies itself over time.
Distinguishing Between Feedback Types
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Note that it is important that in along according to this definition, the polarity of this signal coming to this amplifier it is immaterial. In many of the textbook you might have seen that invariably, we say this is + and this is ‒ and this + and ‒ this sign it may be defining ‒ve feedback system.
Detailed Explanation
The distinction between negative and positive feedback systems is not strictly dependent on the polarity of the signals. Instead, it is essential to look at the effect of the feedback on the original input signal. This means that whether the signals are marked as positive or negative does not inherently dictate the type of feedback; it is the behavior of the feedback that determines it.
Examples & Analogies
This can be likened to different variables in a recipe for baking. Whether you add sugar (positive input) or salt (negative input) can change the flavor, but it’s the balance and combination that determine if the dish is sweet or savory.
Feedback System Responses
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Note that while we are making this change original change and we are trying to see the effect, we are giving sufficient time to see the corresponding steady state change.
Detailed Explanation
In feedback systems, the stability and responses are evaluated not only at the moment of change but also over time to reach a steady state. Understanding how feedback impacts a system in this steady state helps to categorize and analyze systems accurately.
Examples & Analogies
Consider a dimmer switch for a light bulb. When you adjust the dimmer, the bulb takes a moment to reach the desired brightness. The immediate flicker is like the instantaneous response, while the brightness you finally observe is akin to the steady state we analyze in feedback systems.
Key Concepts
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Feedback Systems: Types of systems that use output signals to adjust input.
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Negative Feedback: Reduces output changes to ensure stability.
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Positive Feedback: Increases output changes that can enhance performance but may destabilize.
Examples & Applications
In audio systems, negative feedback can reduce distortion by counteracting unwanted signals.
Positive feedback is used in oscillators to maintain signal generation by amplifying minor signal fluctuations.
Memory Aids
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Rhymes
Negative feedback keeps things straight, keeping systems in a steady state.
Stories
Imagine a seesaw: when one side goes up, the other goes down, just like negative feedback balances the highs and lows.
Memory Tools
Use NERD to remember: Negative Enhances reliability, Reduces distortion.
Acronyms
PEN for Positive feedback
for Propel changes
for Enrich output
for Not stable.
Flash Cards
Glossary
- Feedback System
A system where a portion of the output is fed back into the input to influence the overall output.
- Negative Feedback
A feedback system that counteracts changes in the input signal, leading to stability and reduced distortion.
- Positive Feedback
A feedback system that amplifies changes in the input signal which can lead to increased output response.
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