Introduction to Output Resistance Discussion
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Understanding Input Resistance
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Today, we will discuss how to calculate input resistance in a feedback system. Can anyone tell me what input resistance is?
Is it the resistance that the input source sees?
Exactly! It's crucial in determining how much of the input signal affects the output. What do you think happens when we add load factors?
Does it change the resistance value?
Yes! When we incorporate load transimpedance, we multiply it by an attenuation factor to find the new resistance. We can think of it as the effective resistance seen by the input.
So, the load affects our calculations?
Correct! Always remember, input resistance is critical when analyzing the stability and performance of feedback systems.
Calculating Resistance in Parallel
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let’s delve into why certain resistances are considered in parallel. Who can explain this concept?
Is it because the voltages across those resistors remain the same?
Great point! This is why we need to consider how the input voltage develops in these configurations. What do we mean by an internally developed voltage?
Is that the voltage after including load factors?
Exactly! The internally developed voltage is influenced by the load factors, affecting the overall input resistance. Remember this - parallel configurations can reduce overall resistance.
Importance of Feedback in Resistance Calculations
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let’s talk about feedback resistance. How does feedback influence our calculations?
Does it make our output more stable?
It does! Also, discounting or modifying feedback factors like beta can affect our resistance, which we need to keep constant for accurate calculations. How do you feel about keeping track of these values?
It seems complicated; do we have to remember which values are constant?
Yes! A good mnemonic is 'Beta’s Best' to remember that beta should stay unchanged during certain calculations!
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The discussion focuses on calculating input resistance within feedback systems, emphasizing the effects of load resistance and feedback factors on the overall output resistance. The section also hints at further investigation into related feedback circuits.
Detailed
In this section, we explore the concept of output resistance in feedback systems. The lecture starts with recognizing the input resistance and how it is calculated based on various load conditions. The teacher explains that the input resistance is finite and can be defined using a formula that incorporates load transimpedance and an attenuation factor. It is elaborated that the specific factors affecting input resistance include the feedback circuit, the resistance in parallel, and voltage relationships. Additionally, there was a correction made in the determination of feedback factors, emphasizing an unchanged beta value during operations. The importance of considering various feedback circuits before finalizing the discussion on output resistance is highlighted, setting the stage for in-depth exploration in subsequent parts.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Understanding Load-Affected Trans-Impedance
Chapter 1 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
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 feedback systems, load-affected trans-impedance (Z′) refers to how the input resistance reacts to changes in load conditions. Specifically, 'finite' means that the resistance is measurable and not infinite. The input resistance can be influenced by an attenuation factor, which modifies the original trans-impedance (Z). To accurately assess a feedback system, we must consider these alterations that come from various loads.
Examples & Analogies
Think about a garden hose. When you attach a nozzle (a load), it changes how quickly water flows out (analogous to the input resistance) based on the nozzle's design. The hose's diameter (original impedance Z) and the nozzle's impact (load-affected impedance Z′) need to be considered for effective watering.
Calculating Input Resistance
Chapter 2 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
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 v o which is of course, reduced version of internally developed voltage. So, the v it is Z × i ×.
Detailed Explanation
In analyzing the input resistance, it's crucial to understand that components in parallel share voltage. The output voltage (vo) developed across these components is a reduced form of the internal voltage due to this parallel arrangement. This means that we can derive the input resistance by considering the combination of these resistances and how they affect voltage.
Examples & Analogies
Imagine water flowing through multiple pathways. If two pipes (resistances) are open at the same time (in parallel), the water level (voltage) is distributed between them. To find out how much water goes into each pipe, we have to understand how they work together, just like calculating input resistance in a circuit.
Feedback System Input Resistance Calculation
Chapter 3 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, 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
When calculating the input resistance of a feedback system, we need to include all relevant resistances that act in parallel. Each resistance contributes to the total input resistance, affecting the overall performance of the feedback loop. This comprehensive consideration ensures that our calculations reflect the true behavior of the system.
Examples & Analogies
Think of a group of friends trying to decide where to eat. If everyone expresses their preferences (resistances), the final decision (input resistance) depends on how many people want to go to each option (parallel contributions). By listening to everyone’s choice, the whole group's preference is represented.
Understanding Feedback Consequences on Output Resistance
Chapter 4 of 4
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So far we are talking about input resistance, now we can also see the change in the output resistance before we go into this please let me take a break and then we will see how to derive the corresponding output resistance.
Detailed Explanation
The discussion shifts from input resistance to output resistance, highlighting how feedback influences both aspects. Understanding the changes in output resistance is fundamental for designing effective feedback systems. After a brief pause, examples and derivations of output resistance will be further explored.
Examples & Analogies
Consider an orchestra. The input resistance is like the individual musicians playing their instruments, while the output resistance represents the harmony they create together. Just as music changes based on how musicians respond to each other, output resistance varies based on feedback in the system.
Key Concepts
-
Input Resistance: Defined as the resistance seen by the input source, crucial for feedback systems.
-
Output Resistance: The total resistance at the output, affected by internal and external circuit components.
-
Feedback Effect: Feedback loops can modify resistance values, improving system stability and performance.
Examples & Applications
Example 1: In a feedback amplifier, increasing load resistance decreases the overall input resistance seen by the source.
Example 2: In a parallel circuit configuration, combining input and feedback resistances alters output voltage response.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
See the input, feel the load, resistance tells us where to go.
Stories
Imagine a river (the input) running through various valleys (the resistances) where water levels change based on terrain (feedback factor), helping maintain flow.
Memory Tools
Remember 'R-FLO' for Resistance-Feedback-Load-Output when considering circuits.
Acronyms
FIRE - Feedback Increases Resistance Effectively.
Flash Cards
Glossary
- Input Resistance
The resistance presented to the input of a system, modifying the input signal based on the circuit configuration.
- Output Resistance
The equivalent resistance at the output of a system, which results from the internal resistances and the feedback applied.
- Feedback Circuit
A system design where a portion of the output is fed back to the input to improve system performance.
- Load Transimpedance
A measure of how the output voltage changes concerning the input current when loads are applied.
Reference links
Supplementary resources to enhance your learning experience.