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Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Voltage Gain Calculation
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Let's start by discussing voltage gain in feedback systems. What is voltage gain?
Is it the ratio of output voltage to input voltage?
Exactly! In feedback systems, this gain can be modified. For example, we calculate the gain using values like amplifier gain and feedback factor. Can anyone tell me how we calculate the modified gain, A'?
I think we use the formula A' = A / (1 + Ξ²A).
Great job! That's correct. Remember, Ξ² is the feedback factor. This relationship helps us see how feedback affects overall gain.
What do we expect when Ξ² is high?
Good question! High Ξ² causes a significant reduction in gain. Continuing from where we left off, let's look at how input and output resistances are influenced.
In conclusion, when feedback is applied correctly, it alters our gain effectively.
Input and Output Resistance
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Now, let's focus on input and output resistance. How does feedback impact these resistances?
I remember that feedback reduces output resistance and increases input resistance.
Exactly! For input resistance, we use R in_f = R in(1 + Ξ²A). Why is this important?
It allows us to check how well our amplifier will handle various input signals.
Absolutely! And for output resistance, we typically see it decreasing as well. Can anyone recall an example of how we might calculate this?
Using R out_f = R/ (1 + Ξ²A)?
Exactly! These formulas help us quantify the alterations caused by feedback.
To crystalize this, remember that a higher input resistance is often desirable in amplifiers since it puts less load on the input signal.
Numerical Example Review
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We have covered how feedback affects voltage gain and resistances. Now, letβs recap a numerical example from earlier.
We calculated a feedback gain, right? The initial gain was 200 with a feedback factor of 0.095.
Right! And what did we find the new gain to be?
The new gain came out to be 10 after the calculation.
Wonderful! How about the input resistance in that example?
It increased from 1 kΞ© to 20 kΞ© due to the feedback.
Exactly! You all grasp the concept well. Remember these examples when you tackle similar problems.
Letβs wrap up this exampleβfeedback enhancers can significantly change circuit characteristics.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
In this section, concepts of feedback systems are reviewed, focusing on calculating voltage gain, input and output resistances, and how these parameters are affected by feedback networks. Two numerical examples illustrate ideal and non-ideal feedback scenarios, emphasizing practical applications.
Detailed
In this section of the Feedback System chapter, critical aspects such as voltage gain, input resistance, and output resistance of feedback systems are summarized. The section emphasizes how feedback mechanisms play a crucial role in determining these parameters, with a numerical example for both ideal and non-ideal cases. In the first case, ideal feedback leads to enhanced input resistance and reduced output resistance, showcasing a straightforward calculation process. The second case presents challenges from non-ideal feedback conditions. By using specified values such as amplifier gain and resistance, both cases clarify fundamental feedback system characteristics, demonstrating the significance of understanding feedback in analog circuits.
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Summary of Key Concepts
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To summarize all these 4 sub-lectures, what we have discussed in this topic of feedback system. So far we have talked about basic concepts of the feedback system, there we have introduced how we define the feedback system and then we have talked about 2 basic types of feedback mechanism or feedback system namely, +ve feedback type and βve feedback types feedback system.
Detailed Explanation
In this part, the lecturer summarizes the main topics covered in the previous lectures about feedback systems. They talk about the foundational concepts, specifically defining what a feedback system is. Furthermore, they explain the two main types of feedback mechanisms: positive feedback and negative feedback. Positive feedback amplifies changes or deviations, while negative feedback works to stabilize the system by reducing the effects of any changes.
Examples & Analogies
Consider a thermostat in a house as an example of negative feedback. When the temperature rises above a set point, the thermostat turns off the heater, preventing the space from getting too hot. This stabilizing action illustrates how negative feedback keeps a system operating within a desired range.
Discussion of Feedback Characteristics
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In the subsequent discussion, it is mostly related to βve feedback system. So then, we have talked about transfer characteristic of feedback system namely, feedback system transfer characteristic A = . So also, we have talked about loop gain = β Ξ²A then, desensitivity factor, D = (1 + Ξ²A).
Detailed Explanation
Continuing from the introduction, the lecturer focuses predominantly on negative feedback systems. They discuss the characteristics of these systems in terms of their performance metrics like transfer characteristics (how input signals are transformed to output), loop gain (which indicates how much signal is fed back into the system), and the desensitivity factor (which measures how the system's characteristics are stabilized by feedback). These metrics are essential for understanding how feedback impacts system stability and performance.
Examples & Analogies
Think of a carβs cruise control as a feedback system. When the car goes uphill and slows down, the cruise control detects this (loop gain), and it provides more fuel to maintain speed. If the cruise control system were too sensitive (high desensitivity), any small change in speed would create a lot of adjustments, leading to an unstable ride.
Configurations and Their Characteristics
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Then we have talked about 4 basic configurations which normally it is common in electronic circuits and we have discussed about their characteristic. So these are the enlisted 4 basic configurations we have discussed about how the gain it is getting changed. And also we have talked about how the input resistance and output resistance of the system it is getting changed by the desensitization factor.
Detailed Explanation
The lecturer highlights four fundamental configurations commonly found in electronic circuits using feedback. They emphasize how these configurations alter the overall gain of the system and how factors such as input resistance (the resistance seen by the source) and output resistance (the resistance seen by the load) can be modified by the desensitization factor, which ultimately affects performance and stability.
Examples & Analogies
Consider balancing on a seesaw with friends. If one friend is significantly heavier (implying a high gain), it's harder to balance (input/output resistance). However, if you each adjust your positions evenly (adjusting configurations), it becomes easier to find a stable position, mirroring how feedback can stabilize a circuit.
Numerical Examples and Practical Applications
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And then we have discussed about 2 numerical examples associated with 2 feedback configure different types of configuration starting with ideal situation and then also we have moved to non-ideal situation.
Detailed Explanation
The final part of the discussion reviews two numerical examples that illustrate the application of feedback systems in both ideal and non-ideal scenarios. This helps to concretely demonstrate how feedback systems operate in practice, illustrating the theoretical concepts discussed previously with practical calculations and real-world functionality.
Examples & Analogies
Imagine learning to balance a bicycle. In an ideal situation, if you have perfect balance, you maintain a straight line effortlessly. In a non-ideal situation, you might wobble. By applying some feedback (like steering corrections), you can achieve a straighter path, just like in electrical circuits where feedback helps correct for imperfections in real-world applications.
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 relation of output voltage to input voltage in feedback systems.
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Feedback Factor (Ξ²): Measure indicating the amount of output voltage fed back to the input.
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Input Resistance: Resistance encountered at the amplifier's input port.
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Output Resistance: Resistance the output current faces in an amplifier's output.
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Desensitization Factor: Indicates how much feedback modifies the input and output resistances.
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 ideal feedback system, if the forward amplifier gain is 200 and Ξ² is 0.095, the modified voltage gain, A', can be calculated to clarify feedback's impact.
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If the input resistance of a forward amplifier is 1 kΞ© and feedback is applied, then the new input resistance of the feedback system can be calculated using R_in_f = R in(1 + Ξ²A).
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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Input resistance grows, Output drops low, in circuits we know.
π Fascinating Stories
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Once in a circuit town, Feedback was the hero that came around. It helped amplifiers rise, causing gains without disguise.
π§ Other Memory Gems
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To remember gain formulas: 'A = A minus B times A'. (A minus BG always works!)
π― Super Acronyms
F.I.R.S.T.
- Feedback Increases Resistance
- Decreases Signal temperature.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Voltage Gain
Definition:
The ratio of the output voltage to the input voltage in an amplifier system.
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Term: Feedback Factor (Ξ²)
Definition:
A measure of the portion of output voltage that is fed back to the input of a circuit.
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Term: Input Resistance (R_in)
Definition:
The resistance faced by the input current of an amplifier.
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Term: Output Resistance (R_out)
Definition:
The resistance faced by the output current of the amplifier.
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Term: Desensitization Factor
Definition:
A factor that quantifies how feedback affects both input and output resistances.