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Interactive Audio Lesson
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Feedback System Basics
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Today, weβre discussing feedback systems in analog electronics. Can anyone define what a feedback system is?
Is it a system that takes some output and returns it back to the input?
Exactly! Feedback systems are crucial as they help us control processes and improve stability. They can be positive or negative. Can someone tell me the difference?
Positive feedback amplifies the output, while negative feedback reduces it?
Correct! Negative feedback is typically used for stability in amplifiers. Remember the acronym 'NEG' for Negative Feedback: 'Noticing Error Gain'.
Let's move on to specific calculations of voltage gain next.
Voltage Gain Calculation
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To calculate voltage gain, we use the formula A = A_f / (1 + Ξ²A_f) where A_f is the forward amplifier gain, and Ξ² is the feedback factor. Can anyone provide the values of A_f and Ξ² from our example?
The gain A_f is 200 and the feedback factor Ξ² is 0.095.
Great! Plugging those in, we find the total voltage gain to be what value?
It should be 10!
Correct! Remember that this gain shows the effect of feedback on our input signal.
Input and Output Resistance
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Now, letβs talk about input resistance. The formula we use is R_in_f = R_in * (1 + Ξ²A_f). Why do we use this?
Because feedback increases the input resistance, making the circuit less sensitive to input variations?
Exactly! And what about output resistance? How does feedback affect it?
It reduces the output resistance, right?
Correct! This effect is crucial for maximizing power transfer. Remember the acronym 'OUTPUT' - 'Optimizing Utility Through Underlying Parameters'.
Numerical Examples
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Letβs work through a numerical example together. We have an input signal of 100 mV and need to find the output voltage. What steps do we take?
First, we calculate the output voltage using the voltage gain we found, correct?
Yes! What would the output voltage be if the gain is 10?
It would be 1 V.
Exactly! Always remember the simplicity of these calculations in practical applications.
Introduction & Overview
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Quick Overview
Standard
The section delves into feedback systems, providing examples to calculate voltage gain, input and output resistances, and output voltage for multiple scenarios. It emphasizes distinguishing between ideal and non-ideal feedback networks and understanding the impacts of feedback parameters.
Detailed
Summary of Concepts
In this section, we focus on understanding feedback systems within analog electronic circuits. We will explore numerical examples that guide us through calculations of the feedback system's voltage gain, input resistance, output resistance, and output voltage when a specific input signal voltage is provided. We discuss the parameters of two feedback systems β one ideal, with infinite input resistance and zero output resistance, and another non-ideal with finite values.
Key Points
- Voltage Gain Calculation: The feedback voltage gain is derived from both the forward amplifier gain and the feedback factor.
- Input and Output Resistance: The effects of feedback on input and output resistance are analyzed to illustrate how they are modified by the feedback network.
- Examples: Detailed numerical examples demonstrate the calculations required to determine the output voltage for given input conditions. The importance of distinguishing between ideal and non-ideal feedback systems is emphasized, showing how these differences affect performance metrics.
Overall, this section provides foundational knowledge critical for understanding feedback circuits' behavior and characteristics, structured through practical exercises to reinforce comprehension.
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Objective of the Feedback System Example
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So here we do have numerical example and what is our objective here? It is that we need to find the voltage gain of the feedback system, input resistance, output resistance of the feedback system and the output voltage for an input voltage or the signal voltage of 100 mV.
Detailed Explanation
In this section, the primary goal is outlined: to analyze a feedback system by determining its voltage gain, input resistance, output resistance, and output voltage when given a specific input voltage (100 mV). This sets the stage for the detailed calculations that follow.
Examples & Analogies
Imagine trying to find out how efficient a pump is at pushing water through a garden hose. Just as you would measure the flow speed and resistance to understand the pump's performance, here, engineers measure the feedback system's performance to understand how well it amplifies signals.
Ideal Feedback Network Analysis
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To start with, let me consider this relatively simpler case, case-1 where we consider ideal feedback network having the input resistance it is infinite and its output resistance on the other hand it is 0 as we are generating voltage.
Detailed Explanation
This chunk introduces an ideal feedback scenario, where the input resistance is considered infinite and the output resistance is zero. In practical terms, this means that the feedback network doesn't lose any signal when it enters and has full output capability. It's an ideal situation to simplify calculations.
Examples & Analogies
Think of an ideal road with no speed limits and no obstacles. Vehicles can travel as fast as they can without any slowdowns. Similarly, an ideal feedback network operates without resistance to signal flow, thus amplifying the input fully.
Calculation of Voltage Gain and Input Resistance
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So note that just by this feedback network the input resistance it is getting increased by a factor of 20 which means that if the main amplifier input resistance it was 1 k, the feedback system input resistance it is becoming 20 k.
Detailed Explanation
The feedback network allows the input resistance to increase significantly, in this case by a factor of 20 from the original input resistance of 1 kβ¦ to 20 kβ¦. This increase is an essential feature of feedback systems as it helps in reducing the impact of external loading effects on the circuit components.
Examples & Analogies
Imagine a very quiet room (1 k⦠input resistance) where a whisper is easily heard. Now, if you add soundproofing and enhance the acoustics (feedback network), even the softest sounds can be picked up, making the room feel much more sensitive (20 k⦠input resistance).
Output Resistance Calculations
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So now we obtained input resistance of the feedback system, output resistance of the feedback system and next thing is that what is the output voltage? It is very straight forward.
Detailed Explanation
This chunk concludes the calculations for input and output resistance. The analysis shows how feedback networks modify a circuitβs properties, leading to a straightforward calculation for output voltage based on the previously computed gains.
Examples & Analogies
Consider a public speaker whose voice is amplified through a sound system. The greater the input volume (input resistance), the more clearly their voice is projected (output voltage) to a larger audience. Here, just as the system's settings affect how loudly the speaker can be heard, the feedback circuit's parameters dictate signal amplification.
Comparison with 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.
Detailed Explanation
In this second case, the feedback network's parameters are altered to reflect a non-ideal scenario where both input and output resistances are finite. This presents a more realistic situation, as all systems have some active resistance, relegating ideal conditions more to theoretical discussions.
Examples & Analogies
Imagine a busy street (finite resistance) where cars can travel smoothly but may encounter traffic delays. The ideal condition was like a magically perfect road. The second case illustrates real-world dynamics, showing the need for adjustments based on inherent limitations.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Feedback Systems: Essential for controlling output response by using the output to influence the input.
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Voltage Gain (A): Critical for determining how much an amplifier increases the strength of a signal.
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Input Resistance: Increased by feedback, allowing better handling of input signals.
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Output Resistance: Decreased by feedback to allow better loading characteristics.
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 with a gain of 200 and a feedback factor of 0.095, the calculated voltage gain is 10, leading to an output voltage of 1 V for a 100 mV input.
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In a non-ideal scenario where input resistance is 200 β¦ and output resistance is 4 kβ¦, the voltage gain alters to 6.557 and output voltage adjusts accordingly.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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Feedback loops go 'round and round to stabilize what is found.
π Fascinating Stories
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Imagine an orchestra, where the conductor adjusts volume levels based on feedback from the audienceβs reactionβthis is akin to how feedback systems regulate performance.
π§ Other Memory Gems
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Remember 'RIPE' for remembering feedback benefits: Resistance Increase, Power Export.
π― Super Acronyms
N.E.G. - Noticing Error Gain. This helps recall the concept of negative feedback.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Feedback System
Definition:
A system that returns a portion of the output back to the input to control the process.
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Term: Voltage Gain (A)
Definition:
The ratio of the output voltage to the input voltage in a feedback system.
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Term: Input Resistance (R_in)
Definition:
The resistance seen by the input signal when applying feedback.
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Term: Output Resistance (R_out)
Definition:
The resistance faced by the load connected to the output of the amplifier.
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Term: Feedback Factor (Ξ²)
Definition:
The portion of the output voltage that is fed back into the input.