Input Resistance Correction
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Understanding Input Resistance
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Today we will delve into input resistance correction in feedback systems. To start, can anyone tell me why input resistance is an important concept?
Isn't it important because it affects how much voltage can be accepted and processed by the system?
Exactly! And when we talk about feedback systems, we need to account for factors like load-affected transimpedance, represented as Z'.
How is Z' different from the original Z?
Good question! Z' takes into consideration the attenuation factor, which modifies the original impedance Z to account for feedback effects.
So, if I remember correctly, we really need to differentiate between these two in our calculations?
Yes, and that's critical because incorrect assumptions can lead us to errors in analyzing how the system behaves.
Let's summarize: Input resistance is crucial in feedback systems, and Z' is impacted by the attenuation factor, altering our calculations.
Parallel Resistance Consideration
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Next, let's explore how resistances are configured in feedback systems. Why is it significant to consider them as being in parallel?
Does it have to do with how voltage divides across the resistors?
Right! When resistances are in parallel, the overall input resistance changes, affecting the voltage developed across the system.
Can you explain how we perform the calculations in this case?
Certainly! When calculating input resistance in parallel, we use expressions that combine the resistances, resulting in a formula that provides the correct input resistance value.
To recap: when resistances are in parallel, we must use the appropriate equations to accurately calculate input resistance.
The Importance of Accurate Parameters
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What do you think happens if we mistakenly alter the parameters like R or β in our calculations?
Could it lead to incorrect interpretations of input resistance?
Precisely! For example, if we label β incorrectly as β' instead of keeping it constant, it changes the entire outcome of our calculations.
So, keeping β the same is crucial then?
Exactly! It's essential to ensure that we are using consistent parameters to maintain accuracy in our output.
In summary: Always verify your parameters before finalizing your calculations to obtain the correct response.
Transition to Output Resistance
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We have discussed input resistance, but what is the next logical step in our exploration of feedback systems?
I suppose we would look into output resistance next?
Correct! Understanding how input resistance influences output resistance is key to fully analyzing feedback systems.
What are potential factors affecting output resistance, then?
Good inquiry, as we will see later, things like circuit configuration and external load will play significant roles in shaping output resistance.
Introduction & Overview
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Quick Overview
Standard
In this section, the importance of considering load-affected transimpedance in calculating the input resistance of feedback systems is highlighted. The discussion focuses on how resistance configurations impact input resistance and the need to ensure correct parameters are utilized in calculations.
Detailed
Input Resistance Correction
This section focuses on the calculation and correction of input resistance in feedback systems. The main concept discussed is the load-affected transimpedance, denoted as Z'. This is derived from the original transimpedance, Z, modified by an attenuation factor. The importance of considering resistance values that may be finite is underlined as it influences the results of input resistance calculations.
The discussion also emphasizes that resistances in such configurations come into play in parallel arrangements, which affects the voltage development across the circuit. Key to this, the expression of input resistance changes based on whether load effects are incorporated or not, and shows how to modify the original parameters for accuracy. Finally, the teacher mentions the transition towards discussing output resistance, suggesting a broader analysis of the feedback circuit.
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Input Resistance in Feedback Systems
Chapter 1 of 4
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Chapter Content
Again I have to make this correction and then if I consider this R it is finite. Then the input resistance of the feedback system it will be given by this where Z′ it is load affected trans impedance and look when I say load affected it is basically whatever the attenuation factor we do have here that we need to consider along with the original Z.
Detailed Explanation
In this chunk, the speaker emphasizes the importance of correcting the input resistance calculations in feedback systems. The term 'R' is treated as a finite value. 'Z′' is introduced as the load-affected transimpedance, which means that it takes into account the attenuation factors that affect the original impedance 'Z'. Understanding this helps in accurately calculating the input resistance of the system under feedback conditions.
Examples & Analogies
Think of a water system where different pipes have varying sizes (representing impedance). In a feedback system, if a pipe (impedance) gets narrower due to a valve (load effect), the flow of water (current) passing through adjusts accordingly. Just like we calculate how water flows based on the sizes of pipes and valves, we must account for the load effect on impedance to understand the true input resistance in electronic circuits.
Parallel Resistance Consideration
Chapter 2 of 4
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Chapter Content
So, why we have to consider these are in parallel that is because this resistance and this resistance they are coming in parallel. So, the voltage getting developed here which is vo which is of course, reduced version of internally developed voltage.
Detailed Explanation
The speaker explains that when calculating input resistance, both resistances must be considered as being in parallel. This is important because the voltage developed at the output, denoted as 'vo', represents a reduced version of the internally developed voltage due to the feedback and load conditions. The parallel relationship impacts how we compute the total input resistance of the system.
Examples & Analogies
Imagine two parallel roads (the resistances) connecting to a single bridge (the output voltage). If both roads are used, traffic (voltage) is shared across them, affecting how much can pass through the bridge. This analogy represents how input resistance behaves in parallel configurations: the total input is influenced by all paths available.
Effects of Additional Resistance
Chapter 3 of 4
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Now if I consider this also which means if I consider this resistance also then that resistance also coming in parallel. So, I think that is how we can calculate the corresponding input resistance of the feedback system.
Detailed Explanation
This chunk discusses the additional resistance taken into account when calculating the overall input resistance of a feedback system. By including more resistances in parallel, one obtains a more accurate representation of the input resistance, which reflects all affecting factors in the circuit.
Examples & Analogies
Think of adding more lanes to a highway (more resistances). The more lanes you have, the easier it is for cars to flow through (input current). In electrical terms, considering all resistances in parallel gives a better picture of how the overall system behaves towards the input signal.
Clarifying β Parameter Usage
Chapter 4 of 4
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In this case when I explained that the we do have R here we do have this L resistance and this resistance then the input resistance of the feedback system it is (1 + β ) + R this β of course, it is remain should remain unchanged it should not be β′ because effect of this one I have already considered here.
Detailed Explanation
Here, the speaker clarifies the use of the β parameter in the input resistance formula. The correction states that β should remain constant (not changed to β′) because its effect has already been accounted for in the changes previously discussed. This distinction is crucial for maintaining accuracy in calculations.
Examples & Analogies
Consider the β parameter as a sales tax rate when calculating the total price of an item. If you already include the tax in your calculations, changing it would misrepresent the total cost. Similarly, the speaker is emphasizing that keeping β unchanged is necessary to ensure that the calculations reflect the actual situation in the feedback system.
Key Concepts
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Input Resistance: Refers to how much resistance the input of a circuit presents.
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Load-Affected Transimpedance: The adjusted transimpedance considering the load effects.
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Parallel Resistor Configuration: Describes the arrangement where resistors are connected across the same voltage source.
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Feedback Configuration: The method by which a system uses past outputs to influence current inputs.
Examples & Applications
If a feedback amplifier has a load impedance of 100 Ohms and the original load-affected transimpedance is 200 Ohms, the total input resistance would require the parallel calculation of these values.
In a circuit where feedback is applied incorrectly, such as altering β erroneously, you may wrongly estimate the input response leading to performance issues.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
In feedback systems, oh what a deed, input resistance is what we need!
Stories
Imagine a wise owl, who only accepts signals through a narrow gate—this gate is our input resistance controlling what message comes through!
Memory Tools
Remember the acronym 'PRAISE' to think of Parallel Resistances Affect Input Signal Effectively.
Acronyms
ZAY
Z' Affects Yields—understanding how modified impedance impacts input outcomes!
Flash Cards
Glossary
- Input Resistance
The resistance seen by the input of a system, significant in understanding how circuits will respond to signals.
- Transimpedance
A measure of how much voltage changes in response to current flowing through a circuit.
- Feedback System
A system that uses its output as input in a loop, affecting the overall behavior and response.
- Attenuation Factor
A coefficient representing the reduction of a signal's strength in a feedback system.
- Voltage Divider
A configuration that splits an input voltage into smaller output voltages.
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