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Interactive Audio Lesson
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Understanding Non-Ideal Feedback
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Welcome, everyone! Today, we will explore non-ideal feedback networks. Can anyone tell me what they think a non-ideal feedback network means?
I think it refers to feedback systems that don't have the ideal conditions, like infinite input resistance or zero output resistance.
Exactly! In non-ideal feedback networks, both the input and output resistances are finite. This significantly affects circuit performance. Let's dive into how these parameters are calculated.
Can you remind us what those parameters are?
Sure! We typically assess the voltage gain, input resistance, and output resistance. Remember the acronym 'VIO' for Voltage, Input, and Output resistances. Now, let's look at a specific numerical example.
Numerical Example of Non-Ideal Feedback
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Consider a feedback system with a forward amplifier gain of 200 and a feedback factor of 0.095. Let's calculate the voltage gain of the feedback system.
How do we start?
First, we find the modified gain A', which combines the input resistance and feedback factor. It is given by the formula: Aβ² = A * Load factor. Who can tell me that load factor based on our parameters?
It would be A multiplied by the loading voltage, right?
Correct! Now let's calculate this step-by-step.
Effects on Input and Output Resistance
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When we have non-ideal feedback, how can we express the input resistance with feedback?
Isn't it R_in * (1 + Ξ²A)?
Exactly! This shows how feedback enhances the input resistance. Can anyone explain how output resistance behaves?
I think the output resistance decreases due to shunting effects.
Right! It effectively divides the total resistance. Understanding these relationships is crucial.
Calculating Output Voltage
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Letβs wrap up by calculating the output voltage with the given input of 100 mV. Using the gain we've calculated, how would you find the output voltage?
By multiplying the gain with the input voltage, right?
Exactly! This will give us V_out. Whatβs our outcome if we continue with this?
In this case, it would yield an output voltage of 1V since the gain is 10.
Correct! Great job applying everything we've learned today.
Introduction & Overview
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Quick Overview
Standard
The section delves into a specific case of non-ideal feedback networks, highlighting the differences in voltage gain, input and output resistance, and output voltage as compared to ideal feedback systems. Various calculations and derivations are presented to illustrate how these parameters are affected in a scenario involving finite input and output resistances.
Detailed
In this section from Prof. Pradip Mandal's lecture on Analog Electronic Circuits, we explore the intricacies of a non-ideal feedback network. We begin by establishing the significance of understanding the impact of finite input and output resistance, which deviates from ideal conditions. The use of a numerical example facilitates a deeper understanding of the voltage gain, input resistance, output resistance, and resulting output voltage for a given input signal. The calculations illustrate how the feedback factor modifies these parameters, providing foundational insights into feedback systems in electronic circuits. Notably, the section emphasizes the desensitization factor and introduces techniques for calculating load-affected gains and resistances, thereby reinforcing the relationship between feedback mechanisms and circuit performance.
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Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Non-Ideal Feedback Networks
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Now, if I consider the 2nd case, I should not say it is ideal. So this part may be ideal, but with finite resistance. In fact, we are considering relatively low input resistance. So we are considering non-ideal rather non-ideal feedback, and input resistance it is 200 and output resistance coming in series. So, that is 1 kβ¦. With that we need to find the corresponding feedback system gain input resistance and output resistance.
Detailed Explanation
In this chunk, we are shifting focus from an ideal feedback case to a non-ideal feedback network case. Here, we do not assume infinite input resistance or zero output resistance. Instead, we specify that the input resistance is 200 ohms and the output resistance is 1 kβ¦. This reflects real-world circuits where components have limits, making it crucial to adjust expectations for gain and resistance accordingly.
Examples & Analogies
Think about two different water hoses. An ideal hose has infinite capacity to deliver water without any loss (like ideal feedback), but a real hose might have narrow points that restrict flow (like non-ideal feedback). The capacity (resistance) and flow rate (gain) change based on these restrictions.
Effect of Finite Input and Output Resistances
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So, before we start, let we consider since we do have since we do have finite input resistance and output resistance of the feedback network, the input resistance here it is affecting the output port. So the voltage will be getting here, it is not same as this internal voltage. Rather, we may say that load affected voltage, let me use different color here. So we need to be careful that A it is giving us 200, but Aβ² it is different.
Detailed Explanation
This chunk highlights how the finite input and output resistances impact the overall performance of the feedback network. The internal voltage produced by the amplifier is not the same as the voltage seen at the output due to these resistances. The new voltage gain, termed A', must be recalculated to account for these effects. Thus, while the forward gain A remains at 200, the actual gain observed A' will differ.
Examples & Analogies
Imagine you are trying to hear someone speak while they are standing close to a loudspeaker. The speaker (forward amplifier) produces a loud sound (gain), but because there is noise (finite resistances), you may not hear the person as clearly as you would expect (different Aβ²). This represents the effect of resistance on signal transmission.
Calculating Load-Affected Gain
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So how do we find this Aβ²? So the way we define this Aβ² it is A multiplied by whatever the load we do have here, it may be external or it may be internal part of the feedback network. So in this case, R it is loading. So the loading factor it is = 200 Γ that gives us . So I have some calculation for you. So this is 9.523.
Detailed Explanation
In this section, we delve into calculating the modified gain A' of the feedback network considering the impact of the load resistance. The gain is adjusted based on a loading factor calculated from the forward gain (A) and the loading impact from resistances connected to the output. This shows how practical configurations require careful calculations to assess performance accurately.
Examples & Analogies
Consider a car (the amplifier) driving on a road (the load) where there are speed bumps (the finite resistances). Even though the car's speed is maximum on the highway (the forward gain), the bumps affect how fast it can actually go (loading factor).
Input and Output Resistance Calculations
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Now, we need to calculate the output resistance R. So, now here we do have shunt connection. So the shunt connection it is reducing the resistance which means that the output resistance it will be = = 200 β¦.
Detailed Explanation
The output resistance of the feedback network is impacted by a shunt configuration that reduces the total resistance observed at the output. This chunk gives the specific output resistance value, showcasing how feedback systems can influence output characteristics in non-ideal settings. The formula for calculating R serves as a guide for analyzing how configurations change the output characteristics.
Examples & Analogies
Imagine trying to pull a heavy object (output resistance). If you have a team of people (shunt configuration) working together, pulling in the opposite direction, the overall effort feels reduced, and you achieve a lower resistance to movement.
Output Voltage Calculation
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So that is giving us very simple situation. So the output voltage v it is 10v. So that is giving us 10 Γ 100 mV = 1 V.
Detailed Explanation
Here, the overall output voltage is derived using the modified gain we calculated earlier. By applying a simple multiplication of the gain with the input signal (100 mV), we determine the output voltage. This demonstrates how feedback impacts the effective voltage delivered at the output based on the input and feedback characteristics.
Examples & Analogies
Think of a water tank being filled. If the flow rate (input voltage) is steady at a low level but the tank has a system that amplifies the water flow (gain), the output spout can deliver a significantly larger amount of water (output voltage) based on the initial low flow and the amplification system.
Summary of Non-Ideal Feedback Effects
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So, we do have this number 0.45238 and that is giving us a value which is 2.9047 kβ¦. So earlier the input resistance it was 20 kβ¦. Now that got drastically reduced to 2.9 kβ¦ only.
Detailed Explanation
In summary, when transitioning from ideal to non-ideal feedback systems, all key parametersβinput resistance, gain, and output resistanceβare recalibrated. This change symbolizes real-world applications where ideal conditions rarely exist. The substantial reduction in input resistance illustrates the consequence of finite elements in feedback networks, affecting performance expectations.
Examples & Analogies
Consider a smartphone charging. When the charging cable is of high quality (ideal), it transfers maximum power efficiently (high input resistance). However, using a cheap cable introduces resistance, limiting charging speed (low input resistance) and affecting overall device performance.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Voltage Gain: The enhancement or reduction of voltage in the output compared to the input caused by the feedback mechanism.
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Input and Output Resistance: Characteristics of a circuit affecting how it interacts with external components.
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Desensitization Factor: Key role in determining how feedback influences circuit behavior.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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In a non-ideal feedback network, with a gain of 200 and feedback factor of 0.095, the output is calculated to be 10v for a 100 mV input.
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If the input resistance of a forward amplifier is 1 kβ¦, feedback can increase this to 20 kβ¦ under certain conditions.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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Feedback's a loop, round and round, where added signal is what we've found.
π Fascinating Stories
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Imagine a feedback loop as a well. The water that flows back into the well strengthens the source, much like how feedback helps stabilize circuits.
π§ Other Memory Gems
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VIO: Remember Voltage gain, Input resistance, and Output resistance.
π― Super Acronyms
FIR
- Feedback
- Input
- Output resistances governs the circuit efficiency.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Feedback Factor
Definition:
A parameter that quantifies the portion of output fed back to input in a feedback system.
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Term: Desensitization Factor
Definition:
A measure of how much the overall gain of the feedback system is reduced compared to the open-loop gain.
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Term: Input Resistance
Definition:
The resistance faced by the input signal of a circuit or feedback system.
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Term: Output Resistance
Definition:
The resistance seen by the output load in a feedback system.
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Term: Voltage Gain
Definition:
The ratio of output voltage to input voltage in a circuit.