Professional Courses
Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.
Categories
Interactive Games
Fun, engaging games to boost memory, math fluency, typing speed, and English skillsβperfect for learners of all ages.
Typing
Memory
Math
English Adventures
Knowledge
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introduction to Feedback and Output Resistance
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Today, we will discuss feedback connections in amplifiers, specifically focusing on their impact on output resistance. Can anyone tell me why feedback is important in amplifiers?
Feedback helps stabilize the gain and improve bandwidth.
Exactly! Feedback connections can greatly influence an amplifier's performance. We can categorize feedback in amplifiers, like shunt-series feedback. What do you think this term means?
Isn't it related to how signals are mixed and sampled?
Yes, you are correct. Shunt-series feedback means sampling a voltage in a shunt fashion and applying it in series, affecting the output resistance. Let's review the terms involved.
What are the ideal conditions for feedback connections?
In ideal feedback systems, we assume infinite input resistance and zero output resistance. This simplifies our calculations. Nevertheless, real-world scenarios often introduce finite resistances, making it important to adapt our models.
In summary, feedback can alter the output resistance significantly. Next, we will derive the output resistance mathematically. Remember, R_out and feedback factor Ξ² play key roles.
Deriving Output Resistance Expressions
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Let's derive the output resistance. When we apply a voltage source to the output and measure the resulting current, we get a relationship defined by R_out. Can someone explain how we proceed?
We need to use Kirchhoff's laws to relate voltage and current.
Correct! We assume the internal voltage as A_v and relate it to the feedback current. Applying the feedback factor Ξ² can adjust this relationship. What happens when we have source resistance?
The calculated Ξ² changes, impacting the output resistance!
Exactly! The dependence on R_s alters our output resistance calculations, moving beyond the ideal model. These adjustments are essential in practical scenarios.
How do we take into account the finite resistances in the feedback network?
Good question! Each component's resistance alters the feedback factors we calculated. We must consider these resistances in succession, ultimately leading to a more complex yet realistic model.
To recap, understanding the feedback factors and output resistance interplay is vital for designing effective amplifiers.
Trans-impedance Amplifiers
Unlock Audio Lesson
Signup and Enroll to the course for listening the Audio Lesson
Now letβs switch to trans-impedance amplifiers. How does this configuration differ from our previous examples?
In trans-impedance amplifiers, we have current input and voltage output, right?
That's correct! In essence, itβs the reverse of what we discussed earlier. What can you say about the feedback mechanisms in this setup?
The feedback types remain the same, but the relationship between input and output signals changes.
Absolutely! The configurations might be similar, but the effects on output resistance vary. How do we derive output resistance in this configuration?
We still measure voltage and current, applying similar principles as in voltage amplifiers.
Exactly! We apply the same understanding, while adjusting for the new signal type. Ensuring clarity here helps solidify your knowledge.
To conclude, remember that feedback inherently influences the amplifier's performance and output resistance.
Introduction & Overview
Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.
Quick Overview
Standard
The section delves into the principles of output resistance in voltage amplifiers with feedback connections, exploring both ideal and non-ideal conditions, resistance configurations, and the impact on performance. It also introduces feedback mechanisms in trans-conductance amplifiers, elaborating on how output resistance is affected in these scenarios.
Detailed
Output Resistance and Feedback Connection
In this section, we explore the concept of output resistance in the context of feedback connections applied in analog voltage amplifiers. Specifically, we begin with voltage amplifiers and how feedback influences their output resistance.
Key Concepts:
- Feedback Connection Types: We define feedback configurations such as shunt-series feedback, highlighting their characteristics and effects on circuits.
- Ideal vs Non-Ideal Feedback: An ideal feedback connection assumes infinite input resistance and zero output resistance. However, in practical applications, we consider finite resistances impacting the calculated output resistance.
- Output Resistance Definition: The output resistance is derived by applying voltage to the output port while observing the resulting current, elucidating the significance of feedback on the output port impedance.
- Effects of Source Resistance: The presence of source resistance modifies the feedback factor Ξ², which in turn affects the overall output resistance.
- Trans-impedance Amplifiers: We also examine trans-impedance amplifiers where the output is in current format and the feedback mechanisms are different, yet the analysis remains conceptually similar.
In conclusion, understanding how feedback connections alter output resistance is crucial for designing efficient analog circuits, with implications for performance and stability.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Output Resistance
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, yeah dear students, so welcome back after the short break and before the break we are talking about the change of input resistance of the different configuration. And whereas, we are going to talk about change in output resistance to start with let we consider it is a voltage amplifier and we want to see the change due to feedback connection.
Detailed Explanation
In this section, we revisit the topic of output resistance after previously discussing input resistance. We're focusing on voltage amplifiers and how their output resistance changes when feedback connections are applied. The goal is to understand these changes using an ideal voltage amplifier as a starting point.
Examples & Analogies
Think of an amplifier as a water tap. Just as turning the tap adjusts the water flow, feedback adjusts the amplifier's output, affecting the water pressure (output resistance) at the spout.
Understanding Feedback Connections
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
And since it is voltage amplifier as we have discussed, the circuit is given here. The configuration here it is referred as shunt series feedback or voltage series feedback circuit. And to start with let us consider the feedback network it is ideal namely its input resistance, it is infinite and the output resistance as it is producing voltage, output resistance it is 0.
Detailed Explanation
In feedback circuits, two traits are examined: the input and output resistances. An ideal feedback network has infinite input resistance, meaning it does not draw any current from the input source, and zero output resistance, indicating it can provide maximum voltage to the load. This idealization simplifies the analysis of how feedback affects performance.
Examples & Analogies
Imagine a perfect feedback loop in a restaurant where feedback (customer opinions) comes in infinitely without affecting the chef's performance (input resistance). The chef serves food perfectly every time (output resistance).
Determining Output Resistance
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
However, for the forward amplifier we are considering finite input resistance and finite output resistance. We do have the voltage dependent voltage source A v, v it is appearing at the input of v in the forward amplifier. Now, to know the output resistance what we can do?
Detailed Explanation
In realistic scenarios, both input and output resistances are finite and play a critical role in determining the output performance of the amplifier. The next step is to establish a method for determining the output resistance when a voltage source is applied at the amplifier's output.
Examples & Analogies
This situation is like a car that uses gasoline (input resistance) and outputs exhaust (output resistance). To find out how efficiently the car can run, you need to consider both the quality of gasoline and the exhaust system.
Using KCL to Derive Output Resistance
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, if you see if I consider this is short, then if I consider KCL in this mixer what we are getting it is v, input voltage of the amplifier it is β v. But then v it is same as Ξ²v; v is the voltage appearing at the input port of the feedback circuit and v in this case the moment we connect v here it is v, it is same as v.
Detailed Explanation
Using Kirchhoff's Current Law (KCL), we analyze the feedback circuit to relate the input voltage to the output voltage. The equations reveal that the input voltage is inversely proportional to the feedback, indicating how techniques such as negative feedback stabilize and control output resistance.
Examples & Analogies
Imagine a seesaw where one side is affected significantly by weight ( voltage). The input affects output in the same proportion, just as feedback in an amplifier helps balance the circuit.
Calculating Output Resistance with Source Resistance
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, to get the output resistance; to get the output resistance R out_f in presence of a series resistance called source series resistance called R_s and of course, we have to keep the signal here it is 0, so; that means, it is getting shorted like this.
Detailed Explanation
When a source resistance is introduced, we need to readjust our calculations for output resistance in the circuit. By shorting the signal to simulate zero condition, we redefine the relationship between the input and output voltages, leading to new equations for resistance.
Examples & Analogies
This is like having a water pipe with a narrow section (source resistance). As water flows, you need to account for the constriction when measuring water pressure (output resistance).
Impact of Feedback Network Components
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
Now, if we also have to consider say finite value of this resistance, so if I include say this resistance as well. So, if I consider R of the Ξ² network, R_out_Ξ² then this relationship it will be getting changed and the change it will be R_out_Ξ² is also influenced by how components in the feedback network resist or support the circuit.
Detailed Explanation
The equations for output resistance become more complex as we add additional resistive elements in the feedback paths. Each resistance modifies overall resistance differently, affecting how feedback changes the amplifierβs performance.
Examples & Analogies
Think about a road with speed bumps (feedback components). Each speed bump slows down the car (increases resistance) differently, influencing how fast you can reach your destination (output resistance).
Considerations in Non-Ideal Scenarios
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, we might have observed that the output resistance is increasing due to components in parallel or series, but they also create a cumulative effect on overall performance.
Detailed Explanation
In practical circuits, various non-ideal elements can be present. These affect the output resistance significantly. The total output resistance can increase or decrease, depending on whether components are in series or parallel.
Examples & Analogies
Consider layers of clothing on a winter day. Each layer adds warmth (increased output resistance) but could also restrict movement (decreasing circuit efficiency).
Final Thoughts on Output Resistance and Feedback
Unlock Audio Book
Signup and Enroll to the course for listening the Audio Book
So, in the next slide we will be talking about change of output resistance of a trans-impedance amplifier due to the feedback connection.
Detailed Explanation
The discussion transitions to how output resistance behaves in a different type of amplifier called a trans-impedance amplifier. This sets up the next phase in understanding feedback mechanisms in varied amplifiers.
Examples & Analogies
Just as a versatile mobile phone can serve different functions (like a camera or gaming console) depending on its setup, different amplifiers adjust their output resistance based on their design and connections.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
-
Feedback Connection Types: We define feedback configurations such as shunt-series feedback, highlighting their characteristics and effects on circuits.
-
Ideal vs Non-Ideal Feedback: An ideal feedback connection assumes infinite input resistance and zero output resistance. However, in practical applications, we consider finite resistances impacting the calculated output resistance.
-
Output Resistance Definition: The output resistance is derived by applying voltage to the output port while observing the resulting current, elucidating the significance of feedback on the output port impedance.
-
Effects of Source Resistance: The presence of source resistance modifies the feedback factor Ξ², which in turn affects the overall output resistance.
-
Trans-impedance Amplifiers: We also examine trans-impedance amplifiers where the output is in current format and the feedback mechanisms are different, yet the analysis remains conceptually similar.
-
In conclusion, understanding how feedback connections alter output resistance is crucial for designing efficient analog circuits, with implications for performance and stability.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
-
If we connect a load to a voltage amplifier without feedback, the output resistance might be 2kΞ©. With feedback, this can drop to around 1kΞ©, improving performance.
-
In a trans-impedance amplifier, an input current of 10Β΅A with a feedback of 25 can give an output voltage of 250mV.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
-
Feedback flows, both high and low, through amplifiers, it helps us grow.
π Fascinating Stories
-
Imagine a water pump (amplifier) where feedback (a sensor) keeps track of water flow, ensuring needed adjustments for optimal water level.
π§ Other Memory Gems
-
For Feedback connections: 'FAM' - Feedback, Amplifier, Modify.
π― Super Acronyms
RAVEN
- Resistance
- Amplifier
- Voltage
- Effects
- Network.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
-
Term: Output Resistance (R_out)
Definition:
The resistance seen by the load connected to the output of an amplifier.
-
Term: Feedback Factor (Ξ²)
Definition:
A coefficient that quantifies the portion of output used in feedback; influences performance.
-
Term: Transimpedance Amplifier
Definition:
An amplifier that converts input current into output voltage.
-
Term: ShuntSeries Feedback
Definition:
A feedback configuration where voltage is sampled from a shunt path and applied in series.
-
Term: Voltage Amplifier
Definition:
An amplifier designed to increase the voltage of a signal at its output.