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Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Feedback Systems
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Today, we're starting with feedback systems, particularly the four basic configurations of negative feedback. Who can tell me what they remember about feedback systems?
I remember that feedback can either increase or decrease system gain!
Exactly! Negative feedback typically decreases gain but improves stability and bandwidth. Now, can someone explain what desensitization means?
It's when the circuit's performance becomes less sensitive to component variations due to feedback.
Great! That's a key point. Remember, feedback is like a safety net in circuits that stabilizes performance.
Circuit Diagram Analysis
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Letβs look at the circuit diagram of a voltage amplifier with shunt-series feedback. Who can explain what 'shunt-series' means?
Shunt means the feedback connection is parallel to the input, while series means it affects the output.
Exactly! This configuration helps us analyze how input and output resistance change. What do we assume in an ideal scenario?
We assume the input resistance is infinite and the output resistance is zero.
Correct! This ideal assumption simplifies our calculations significantly.
Derivation of Input Resistance
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Now letβs derive the input resistance of a feedback system. Can anyone start with the basic definition?
The input resistance is defined as the ratio of input voltage to input current!
Right! If we apply a signal to our circuit, we can express the total voltage as a sum of our voltage input and feedback voltage. What does this lead to?
It leads to an equation that incorporates the gain of the amplifier and the feedback factor.
Exactly! The feedback system increases the effective input resistance by a desensitization factor, which we represent mathematically.
Practical Scenarios
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Now let's consider practical situations. How does a finite load resistance change our calculations?
It reduces the available voltage at the output, impacting the feedback voltage.
Correct! We need to adjust our equations to account for this load. Remember, the goal is to see how feedback maintains performance despite these realities.
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 interaction between feedback systems and amplifier characteristics, specifically how feedback influences input and output resistance. It covers both ideal and practical scenarios, providing mathematical expressions and circuit diagrams to illustrate these concepts.
Detailed
Circuit Diagram and Initial Conditions
This section primarily explores the effects of feedback systems on input and output resistance within analog electronic circuits. It emphasizes the importance of understanding both the circuit diagram and the initial conditions of the system to analyze the input and output resistance accurately.
Key Concepts Covered
- Feedback Systems: The four basic configurations of negative feedback are outlined, and their implications on system gain, desensitization factor, input resistance, and output resistance are discussed.
- Circuit Diagram Explanation: A circuit diagram exemplifying a voltage amplifier with series voltage feedback is presented. Understanding this diagram is crucial as it lays the groundwork for further discussions about changes in resistance.
- Derivation of Input Resistance: The derivation of the feedback system's input resistance is examined under ideal conditions and how practical scenarios affect this resistance.
- Mathematical Relationships: The relationships involving output resistance and the impact of finite load resistance are elaborated. New expressions for feedback networks that include load effect are derived.
- Transconductance Amplifiers: The section also introduces transconductance amplifiers and explores feedback systems in these contexts, showing how the principles established for voltage amplifiers also apply differently to current-based systems.
By grasping these concepts, students will better understand the behavior of feedback systems in electronic circuits and how they adjust circuit performance.
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Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Feedback Systems
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In the next slide we do have the corresponding circuit diagram here and to start with let we consider a voltage amplifier and its feedback connection it is shunt-series or you can see voltage-series feedback; which means that this port it is shunt and here we do have a series connection here.
Detailed Explanation
This chunk introduces the concept of feedback systems using a voltage amplifier. The feedback connection is identified as shunt-series, which indicates that the feedback is being applied in parallel with the input (shunt) and in series with the output. This setup is important as it shows how the feedback configuration affects the overall circuit behavior.
Examples & Analogies
Imagine a basketball player practicing shooting hoops. If a coach (feedback) stands next to them and gives tips (shunt) while they shoot (series), the player might adjust their technique based on the immediate feedback, thereby improving their shooting performance over time.
Ideal Situations in Feedback Systems
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However, to start with for feedback network let we consider it is ideal situation namely; it is input resistance it is infinite and the corresponding output resistance here it is 0.
Detailed Explanation
In this chunk, the concept of ideal feedback conditions is discussed. An infinite input resistance means that the feedback network does not draw current, which is ideal for maximizing performance. A zero output resistance implies that the feedback can supply all necessary current without any loss. These assumptions help simplify calculations and model the ideal behavior of feedback systems without practical losses.
Examples & Analogies
Think of a perfect sponge that absorbs all the water (infinite input resistance) without dripping any (zero output resistance). If you had a tool that could absorb and utilize all the available water effectively without losing any, that would be the ideal case of feedback in a system.
Deriving Input Resistance with Feedback
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Now, to get this derivation of this input resistance of the feedback system let we consider that we are stimulating the circuit with a signal source called v and we are observing the corresponding current entering into the port and let we call this as i.
Detailed Explanation
This portion begins the derivation of the input resistance of the feedback system. It states that we will apply a signal (v) to the circuit and measure the current entering at the input port. By studying this relationship, we can derive the new input resistance that includes feedback effects.
Examples & Analogies
Consider filling a bucket with water where the input signal (v) represents the water added, and the current (i) is how much water actually enters the bucket. If you have a system in place to efficiently manage the amount of water (feedback), you can predict how full the bucket will be based on the rate of flow (current).
Effect of Finite Resistors in Practical Situations
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Now, let we consider that in practical situation where definitely there may be a finite load R and due to which the voltage available here at this port it may not be same as internally developed voltage.
Detailed Explanation
In real-world applications, the simplicity of ideal conditions often doesn't hold true. Here, the effects of finite resistances in circuits, such as a load resistance (R), are discussed. A finite load affects the voltage present at the circuit's input, demonstrating that actual circuits often behave differently than idealized models.
Examples & Analogies
Imagine a car engine that is designed to run at maximum efficiency under ideal conditions (ideal circuit). However, when you drive it up a hill (load), the engine has to work harder, and its performance (voltage) drops. This reflects how actual systems often need to account for various loads and resistances present in practical applications.
Final Input Resistance Expression
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So, we may say that the corresponding expression of v it will be say ... And from that we can see this is equal to v + Ξ²Aβ² v ... So, we can say that this is v = i R (1 + Ξ²Gβ²).
Detailed Explanation
This section wraps up the derivation process by highlighting how the input resistance expression incorporates feedback factors. The final form of the equation shows how the presence of feedback (expressed through Ξ² and Aβ²) modifies the input resistance to better suit real-world applications.
Examples & Analogies
Think of a smart thermostat that learns and adjusts your home's temperature (feedback). The final temperature setting adjusts based on your preferences (input resistance), taking into account how often you're home (feedback effect). Similarly, the adjusted input resistance accounts for feedback in practical circuits.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Feedback Systems: The four basic configurations of negative feedback are outlined, and their implications on system gain, desensitization factor, input resistance, and output resistance are discussed.
-
Circuit Diagram Explanation: A circuit diagram exemplifying a voltage amplifier with series voltage feedback is presented. Understanding this diagram is crucial as it lays the groundwork for further discussions about changes in resistance.
-
Derivation of Input Resistance: The derivation of the feedback system's input resistance is examined under ideal conditions and how practical scenarios affect this resistance.
-
Mathematical Relationships: The relationships involving output resistance and the impact of finite load resistance are elaborated. New expressions for feedback networks that include load effect are derived.
-
Transconductance Amplifiers: The section also introduces transconductance amplifiers and explores feedback systems in these contexts, showing how the principles established for voltage amplifiers also apply differently to current-based systems.
-
By grasping these concepts, students will better understand the behavior of feedback systems in electronic circuits and how they adjust circuit performance.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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Example 1: In a voltage amplifier circuit, applying feedback lowers the gain but improves linearity and stability.
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Example 2: In a transconductance amplifier, the conversion of voltage to current allows for different feedback adjustments.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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Feedback brings clarity, stability does it create, less sensitive we stand, when components start to variate.
π Fascinating Stories
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Imagine a stabilizing force in a river; as feedback flows, it smooths out rough waters, allowing every boat to sail smoothly. Without it, chaos reigns, and boats capsize over rapid currents.
π§ Other Memory Gems
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Use the acronym 'FIRM': Feedback increases Reliability and stability in a system while moderating its Gain.
π― Super Acronyms
RIG
- Remember Input Gain rules with feedback - itβs reduced for stability.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Negative Feedback
Definition:
A feedback loop that reduces output due to an inverted input signal, enhancing stability.
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Term: Input Resistance
Definition:
The resistance seen by the input signal at the input terminals of a circuit.
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Term: Output Resistance
Definition:
The equivalent resistance at the output of a circuit.
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Term: Desensitization Factor
Definition:
The measure of how less sensitive a circuit is to parameter variations due to feedback.
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Term: Voltage Amplifier
Definition:
An amplifier that increases the voltage of a signal.
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Term: Transconductance Amplifier
Definition:
An amplifier that converts input voltage to output current.