93.1.8 - Numerical Examples
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Understanding Feedback in Amplifiers
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Today, we're going to discuss how feedback connections affect the performance of amplifiers. Can anyone explain what we mean by feedback in this context?
Feedback is when part of the output is fed back to the input, right?
Exactly, Student_1! Feedback can be positive or negative, but we're mainly concerned with negative feedback for stabilization and performance improvement. Now, can anyone tell me about the typical effects of feedback on input resistance?
Negative feedback usually increases input resistance and decreases output resistance.
Correct! Hence, feedback effectively stabilizes the gain of an amplifier. Remember the acronym I.D.E.A. – Input increases, Decreases output, Enhances stability, and Amplifies overall performance!
That’s a useful acronym, Teacher!
Great! Let's move on to numerical examples to see these concepts in action.
Numerical Example Analysis
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"Let's analyze a numerical example. We have given:
Case Study - Non-Ideal Feedback
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Now, let’s explore a non-ideal situation where we have finite input resistance. Can anyone guide us through this calculation?
In a non-ideal case, we need to consider the source resistance. It changes how we calculate v_in and v_out.
Exactly, Student_2! Here, we would still use the same voltage gain formula, but we must account for fixed resistances affecting feedback.
So, it’s essential to consider how source resistance R_s affects the output...
Yes! Keep in mind R_out_f will also change due to feedback factors. How does that affect our expressions?
We can see that R_out_f gets affected as it changes with R_s!
Very well understood! Let’s summarize this before we move on.
In non-ideal cases, feedback influences not only our voltage gain but also the dynamic resistances at play due to the presence of finite resistances!
Introduction & Overview
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Quick Overview
Standard
In this section, we review numerical examples concerning voltage amplifiers and feedback networks. It elaborates on how to calculate voltage gain, input resistance, and output resistance under both ideal and non-ideal conditions using given parameters.
Detailed
Numerical Examples
In this section, we focus on practical numerical examples that provide insights into the effects of feedback connections within voltage amplifiers, specifically analyzing how feedback influences input resistance and output resistance. We will explore how to calculate voltage gain, determine both the input resistance of feedback networks, and evaluate output resistance while considering ideal and non-ideal circumstances.
Key Concepts:
The section is crucial as it assists students in applying theoretical knowledge in practical situations by breaking down complex calculations into understandable processes.
- Voltage Amplifier Dynamics: We study a voltage amplifier where input and output resistances may change due to feedback.
- Feedback Networks: The feedback factors such as β and the effects introduced by finite source resistances are calculated to help understand real-life amplifier behavior.
- Numerical Examples: Two primary cases are considered – one with ideal feedback conditions and another with limitations due to finite resistances. These examples highlight the practical application of theories learned previously.
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Introduction to the Numerical Example
Chapter 1 of 4
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Chapter Content
So, we do have some interesting numerical examples also to have seen starting example it is a voltage amplifier, we do have a voltage amplifier here. So, this is the forward amplifier and the feedback along with its feedback connection of course, the feedback it is shunt here and series here; that means, voltage-series feedback connection.
Detailed Explanation
This chunk introduces a numerical example related to a voltage amplifier. The term 'voltage-series feedback connection' indicates that the feedback circuit is designed to enhance the voltage gain of the amplifier by taking some output voltage and feeding it back into the input. This process can improve linearity and stability in the amplifier's performance.
Examples & Analogies
Imagine you have a microphone (the voltage amplifier) that needs to be amplified to reach an audience. The speaker hears the amplified sound (output), but to keep it clear and stable, a portion of that sound is sent back to the microphone for adjustments. This is essentially what feedback does in our numerical example.
Parameters of the Voltage Amplifier
Chapter 2 of 4
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Chapter Content
The given parameters are here, input resistance it is 1 k, output resistance it is 4 k, A the gain of the forward amplifier in ideal condition it is 200. On the other hand for the feedback circuit the β = 0.095 of course, this is converting voltage to voltage. So, it is unit less.
Detailed Explanation
This chunk presents important parameters for the voltage amplifier example. The input and output resistances (1 kΩ and 4 kΩ, respectively) are crucial for understanding how the amplifier interacts with the circuit it is part of. The gain 'A' represents how much the input voltage is amplified (200 times in this case), which is significant for how much louder a sound might be. The feedback factor 'β' (0.095) shows the fraction of output voltage fed back to the input, which is essential for understanding how feedback affects performance.
Examples & Analogies
Think of a garden hose attached to a water source. Here, the input resistance represents how easily water enters the hose, and the output resistance is how easily it can leave the hose into the garden. The gain reflects how much pressure the water builds up as it passes through. The feedback factor is like a valve that controls how much of the water flowing out is redirected back into the hose to maintain pressure.
Calculating Voltage Gain
Chapter 3 of 4
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Chapter Content
We need to find the value of the voltage gain from the primary input to the primary output defined as denoted by A and defined by . So, we need to find what will be this ratio.
Detailed Explanation
In this chunk, we are tasked with calculating the actual voltage gain, represented by A. To find this, we typically use the formula that combines the amplifier's gain and the feedback factor. The effective voltage gain reflects how much the output voltage compares to the input voltage.
Examples & Analogies
If we think of the voltage gain like a performance enhancement in a concert, it signifies how the sound intensity (voltage output) compares to the original sound (input). Just as a singer's voice can be amplified many times louder than when sung alone, the voltage gain in an amplifier indicates how much more powerful the output is compared to the input.
Case I: Ideal Feedback Network
Chapter 4 of 4
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Chapter Content
Case-I; when you consider feedback network it is ideal one and case-II where feedback network it is having finite input resistance and also it is having finite output resistance.
Detailed Explanation
This chunk outlines two scenarios for analyzing the voltage amplifier. In Case I, we assume an ideal feedback network where both the input and output resistances of the feedback network are infinite, meaning they do not affect the amplifier's performance. This ideal scenario is a simplified version to understand how feedback influences gain without real-world limitations. Case II introduces non-ideality, where finite resistances begin to influence performance, and this is crucial for deeper analysis.
Examples & Analogies
Consider a perfect echo in a large auditorium (ideal feedback scenario), where sound reflects without any loss. In case II, imagine that some sound gets absorbed by the walls (finite resistances), and the echo starts to fade. Understanding both scenarios helps us appreciate how ideal designs differ from practical applications.
Key Concepts
-
The section is crucial as it assists students in applying theoretical knowledge in practical situations by breaking down complex calculations into understandable processes.
-
Voltage Amplifier Dynamics: We study a voltage amplifier where input and output resistances may change due to feedback.
-
Feedback Networks: The feedback factors such as β and the effects introduced by finite source resistances are calculated to help understand real-life amplifier behavior.
-
Numerical Examples: Two primary cases are considered – one with ideal feedback conditions and another with limitations due to finite resistances. These examples highlight the practical application of theories learned previously.
Examples & Applications
Calculating voltage gain with an input resistance of 1 kΩ and output resistance of 4 kΩ.
Exploring changes in output resistance due to feedback in a non-ideal amplifier.
Memory Aids
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Rhymes
Gain the brain, push output’s lane, with feedback in the game!
Stories
Imagine a teacher who always seeks feedback from her students. She adjusts her lessons based on their preferences—this is like an amplifier adjusting its gain according to the feedback received!
Memory Tools
R.I.G.H.T for feedback's impact: Resistance increases, Gain stabilization, Higher stability, Troubleshooting aids.
Acronyms
F.A.C.E
Feedback Adjusts Circuit Efficiency!
Flash Cards
Glossary
- Voltage Gain (A)
The ratio of the output voltage to the input voltage in an amplifier.
- Feedback (β)
A fraction of the output signal that is fed back to the input for regulation.
- Input Resistance (R_in)
The resistance seen by the input signal at the amplifier's input terminal.
- Output Resistance (R_out)
The resistance offered by the amplifier at its output terminal.
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