Practical Considerations - 91.5.2 | 91. Feedback system (Part-B) | Analog Electronic Circuits - Vol 4
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Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Configurations of Feedback Systems

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0:00
Teacher
Teacher

Welcome class! Today we’re diving into the various configurations of feedback systems. Can anyone tell me what feedback systems are?

Student 1
Student 1

Are they the systems that use the output to control the input?

Teacher
Teacher

Exactly! Feedback systems essentially take the output signal and feed it back as an input to modify the system's behavior. Now, we have different configurations like shunt-series and series-shunt feedback systems. Who can explain what shunt means?

Student 2
Student 2

I think shunt refers to connecting in parallel?

Teacher
Teacher

Correct! And series means connecting in sequence, right? These configurations affect how we model the response as we deal with either voltage or current signals. Remember, in shunt configurations we minimize loading effects!

Student 3
Student 3

Why is minimizing loading effects so important?

Teacher
Teacher

Good question! Minimizing loading effects ensures that our feedback signals accurately represent the intended values without distortion. Let's summarize: shunt configurations are parallel, and they help in reducing loading effects!

Voltage and Current Feedback Systems

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Teacher
Teacher

Now, moving on, let’s consider feedback systems with voltage inputs and outputs. Can anyone explain what happens in these setups?

Student 4
Student 4

In voltage feedback systems, we sample the voltage in parallel and mix it in series, right?

Teacher
Teacher

Exactly! And what are the implications of having infinite resistances in these cases?

Student 1
Student 1

It would mean no loading effect, allowing accurate signal representation!

Teacher
Teacher

Correct! Conversely, with current feedback systems, we reverse it. Can you explain how?

Student 2
Student 2

In current feedback systems, we have a series sampler and a parallel mixer, maintaining similar principles!

Teacher
Teacher

Well done! So, we switch the approach entirely based on whether we're dealing with voltages or currents. Remember, appropriate resistances are vital for ensuring we minimize losses. Let's summarize: voltage systems sample in parallel, current systems in series.

Transconductance and Transimpedance Feedback Systems

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Teacher
Teacher

Great! Now let’s talk about transconductance feedback systems. Explaining this to the class requires careful consideration of these terms. Who remembers what transconductance means?

Student 3
Student 3

Doesn't it involve converting voltage into current?

Teacher
Teacher

Yes, and conversely, we have transimpedance systems which convert current into voltage. This is essential as we calculate gains. What do we focus on here?

Student 4
Student 4

The consistency of units between Gm and Ξ², right? To maintain coherence!

Teacher
Teacher

Perfect! If we factor these together, we maintain a unitless system. Always remember, careful conversion reflects our operational integrity. Let’s summarize: transconductance converts voltage to current, while transimpedance does the reverse.

Practical Considerations in Feedback Systems

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Teacher
Teacher

Now, let’s apply what we've learned into practical considerations. Why do we consider real-world resistance in our calculations?

Student 1
Student 1

Because real-world components create loading effects that deviate from our ideal assumptions?

Teacher
Teacher

Precisely! It’s crucial to assume finite resistance can shift performance measures. How might we evaluate these impacts?

Student 2
Student 2

We could create circuit models to empirically test their responses against ideal conditions.

Teacher
Teacher

Exactly! Building and testing models reveals operational stability and helps in recognizing scenarios that deviate from theoretical expectations. Let's wrap up: while ideal situations are valuable, real-world applications challenge us to think critically.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section discusses the various configurations of feedback systems using voltage and current, including their practical considerations and implications on performance.

Standard

In this section, the focus is on the practical applications of feedback systems, detailing different configurations involving either voltage or current signals. The implications of load resistance and circuit conditions are thoroughly explored, highlighting how they affect system behavior.

Detailed

Practical Considerations

This section details the practical aspects of feedback systems in electronic circuits, especially focusing on configurations that utilize either voltage or current signals. As we delve into each configuration, we delineate the typical scenarios where either incoming or outgoing signals are assessed as voltages or currents.

Key Configurations Discussed:

1. Shunt-Series Feedback Systems

  • Voltage signals at both input and output:
  • The feedback signal is sampled in parallel (shunt connection) and mixed in series.
  • This configuration maintains an ideal situation with infinite input resistance () and zero output resistance (Ro), minimizing loading effects.

2. Series-Shunt Feedback Systems

  • Current signals at both input and output:
  • The sampler uses a series connection while the mixer employs a parallel connection.
  • Similar assumptions about resistances hold true to maintain an ideal feedback system.

3. Transconductance Feedback Systems

  • Voltage input & Current output:
  • Like a combination of transconductance (Gm) and feedback resistance, with implications of ideal versus non-ideal models affecting the output.

4. Transimpedance Feedback Systems

  • Current input & Voltage output:
  • Defined similarly to other configurations with a focus on ensuring that loading effects are minimized through appropriate impedance considerations.

The significance of choosing the correct configurations lies in their effects on performance metrics such as gain stability and response sensitivity under varied operational conditions. The section emphasizes that, despite aiming for the ideal conditions, real-world applications may introduce variations that require further evaluation, especially considering feedback paths and loading effects.

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Analog Electronic Circuits _ by Prof. Shanthi Pavan
Analog Electronic Circuits _ by Prof. Shanthi Pavan

Audio Book

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Ideal Situations in Feedback Systems

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So far we have talked about the ideal situation. Now, of course the situation whenever we consider practical examples there we will see that we will not be having any guarantee to have this situation or maybe the other situation.

Detailed Explanation

In the ideal world, we assume feedback systems operate under perfect conditions. However, in real-life scenarios, these perfect conditions often do not exist. Factors like resistance can affect performance. Thus, while we discuss scenarios with ideal components yielding perfect results, we must also consider practical cases where variations in component values might alter the behavior of the feedback system.

Examples & Analogies

Think of a perfectly balanced seesaw at a playground. In theory, if both sides are equal, it works smoothly. But what happens when one side becomes heavier with a friend sitting down? The seesaw tilts and doesn't operate as β€˜ideally’ anymore, just like feedback systems under practical conditions.

Impacts of Finite Resistance

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So, in case say we do have finite value of resistance so, in case this is nonzero likewise in case if we do have output resistance which is nonzero and still if I say that this is infinite and this resistance is 0 this is having 0 conductance.

Detailed Explanation

In practice, if the resistances involved in the feedback system are finite (meaning they have measurable values rather than being zero or infinite), this changes the system's behavior. For instance, if there's resistance at the output, the voltage behavior may differ from expected outcomes. Thus, adjustments must be made to account for these non-ideal conditions.

Examples & Analogies

Imagine trying to pour water from a wide bottle into a narrow one. If you shake the wide bottle (representing the feedback system) with enough force, it might spill (i.e., the output is affected). The 'narrow' represents non-ideal conditions due to resistances which alter the fluid flow, mirroring how non-zero resistance alters feedback performance.

Effects of Loading in Feedback Systems

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If we have a practical load then we have to consider that situation.

Detailed Explanation

In a feedback system, loads (external resistances) can affect how input signals are processed. When you have a load connected, the entire feedback loop's performance alters because the load affects the voltage or current levels being sensed and fed back. This must be calculated to ensure the system operates as intended.

Examples & Analogies

Consider a car on a hill. If the road is perfectly flat (ideal), the car moves without resistance. However, if a steep slant (load) is introduced, it requires more effort (input power) to move. Just like feedback systems, additional loads must be accounted for, in practice, so we can predict how far and fast the car (or system) can operate.

Effect of Desensitization Factor

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So, but then in case if I am having some finite resistance here. So, suppose this is non-infinite.

Detailed Explanation

When systems have finite resistance, the input resistance and output resistance aren't merely the sum of their isolated values but are affected collectively by a factor known as desensitization. This adjustment integrates the interaction through the feedback network, thus providing a modified operational characteristic that helps predict system behavior more accurately.

Examples & Analogies

Think of a team working on a project. If everyone works separately, they achieve individual results, but when they collaborate (like feedback), the output is modified by their interactions. Similarly, if one aspect (resistance) changes, it affects the total project result (system output). This interdependence is what desensitization captures in feedback systems.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Feedback System: A circuit design that modifies its output based on its input for improved stability.

  • Shunt-Series vs Series-Shunt: Differentiates between configurations where signal is sampled in parallel (shunt) or in series.

  • Transconductance (Gm): Converts voltage inputs to current outputs.

  • Transimpedance (Z): Converts current inputs to voltage outputs.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • In a voltage feedback system, the output voltage is sampled and modified using a series mixer to improve signal quality.

  • In a current feedback system, current signals are directly fed back to the amplifier to minimize output impedance.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • In feedback loops do not forget, load resistances play their part, to ensure signals never depart!

πŸ“– Fascinating Stories

  • Imagine a series of rivers (series connections) and lakes (shunt connections) where the water (signal) flows seamlessly without interruption, sampling from each body to adjust the flow downstream.

🧠 Other Memory Gems

  • To remember shunt vs. series: 'S for Shunt is for Sample, S for Series is for Sync!'

🎯 Super Acronyms

Gm = Go, It Means Gain's Monoxide! Utilizing voltage to create currents smoothly.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Feedback System

    Definition:

    A system that utilizes its output to regulate its input to improve stability and performance.

  • Term: Shunt Connection

    Definition:

    A parallel connection that allows a signal to bypass a component.

  • Term: Series Connection

    Definition:

    A connection in which components are linked one after another, ensuring the same current flows through them.

  • Term: Voltage Sampler

    Definition:

    A device that takes voltage samples from a circuit for processing.

  • Term: Current Sampler

    Definition:

    A device designed to sample an electrical current from a circuit.