93.1.4 - Trans-Impedance Amplifier Feedback Configuration
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.
Introduction to Trans-Impedance Amplifiers
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Today, we're discussing trans-impedance amplifiers. Can someone tell me what a trans-impedance amplifier does?
It converts current to voltage.
Correct! The primary function is to take an input current and output a corresponding voltage signal. Now, what happens when we introduce feedback into this system?
The output resistance changes?
Exactly! Feedback affects the output resistance, and it's crucial to understand how this works. Remember, 'feedback fortifies'—this will help you recall that feedback strengthens our system performance.
Can you explain how we calculate the output resistance?
Sure! We can stimulate the output port and measure the current, which helps us derive the output resistance formula. Let's dive deeper into that in our next session.
Output Resistance and Feedback Impact
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
We learned that feedback influences the output resistance. How can we differentiate between ideal feedback and non-ideal feedback?
Ideal feedback has infinite input resistance and output resistance of zero.
You're right! In non-ideal scenarios, both the input and output resistances may be finite. Let’s derive how this affects output resistance mathematically. What do you think would happen if we introduce a finite source resistance?
The total output resistance increases, right?
Exactly! Incorporating these resistances into our calculations allows us to more accurately predict circuit behavior under real conditions. Now, let’s summarize these concepts.
Feedback configuration modifies our output resistance significantly. 'R'= resistance, β = feedback factor—keep these in mind for calculations.
Practical Applications and Examples
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let’s now discuss practical applications of the trans-impedance amplifier configuration. How might this be used in real circuits?
In sensor applications? They often output current signals.
Exactly! Sensors can directly interface with trans-impedance amplifiers to convert the current output into usable voltage signals. Also, can anyone explain why choosing the right feedback configuration matters?
To ensure accurate signal conversion and low noise?
That's correct! A proper feedback configuration minimizes error and maximizes fidelity in signal processing. Always remember: 'trans-impedance trumps noise'! Now, we'll solve a practice example together.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section discusses the principles behind the trans-impedance amplifier feedback configuration, illustrating how output resistance changes with feedback. It focuses on ideal and non-ideal situations, analyzing both voltage and current configurations and how they affect performance.
Detailed
Trans-Impedance Amplifier Feedback Configuration
In this section, we explore the feedback mechanism in trans-impedance amplifiers, commonly used to convert input current signals to output voltages. The discussion begins with reviewing the shunt feedback connection utilized for these amplifiers and its significance in analyzing output resistance.
Key points covered include:
1. Ideal Conditions: It starts with an ideal feedback network where input resistance is infinite while output resistance is zero. The output resistance is determined by stimulating the output port and calculating the corresponding current.
2. Non-Ideal Conditions: The discussion advances to include practical scenarios where both input and feedback network resistances are finite. This analysis reveals how these resistances impact the total output resistance. Various configurations—current to voltage and voltage to current—are explored, showing their relevance in real-world applications.
3. Mathematical Derivations: The section provides expressions for output resistance in both ideal and non-ideal situations, enhancing comprehension through step-by-step derivations.
4. Examples and Applications: Various configurations and scenarios illustrate the concepts, ensuring students understand how to apply this knowledge in practical circuit design and analysis.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Introduction to Trans-Impedance Amplifier Feedback
Chapter 1 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, here we do have the circuit. So, this configuration is given here, it is at the sample side we do have shunt connection and also at the mixer we do have shunt and hence it is called shunt feedback configuration or we may say that here we do have the signal in the form of voltage and the signal here it is in the form of current. So, we are having this voltage shunt-shunt feedback system.
Detailed Explanation
In this chunk, we introduce the concept of a trans-impedance amplifier configured with feedback. In this configuration, the feedback network is arranged as a shunt connection at both the sampling and mixing points. This means that the output signal at the mixer is influenced by the current flowing through it, while the input signal at the sampling side is in voltage form. The use of 'shunt feedback' allows precise control over the amplifier's output by returning part of the output signal back to the input, thus allowing the amplifier to adjust its performance based on the feedback received.
Examples & Analogies
Think of a trans-impedance amplifier as a smart thermostat in your home. Instead of just simply turning on the heating or cooling (the output), it takes the temperature reading (current signal) into account and adjusts its settings (voltage feedback) accordingly to maintain a comfortable environment. This feedback loop ensures the system is responsive and efficient, just like the feedback in the trans-impedance amplifier.
Output Resistance Calculation Under Feedback
Chapter 2 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Now, in this system to get the output resistance, the you know we are stimulating this output port by v as we have done before and we like to observe the corresponding current entering to the circuit and then we have to take the ratio of this. But while we are doing this exercise we have to keep in mind that input port; input port should be supportive for this exercise namely we have to take the signal here it is 0 and in ideal condition it is it is having 0 conductance of this not on equivalent representation of the signal source.
Detailed Explanation
Here, we focus on how to calculate the output resistance of the trans-impedance amplifier. The output port is stimulated by an input voltage (v), and we measure the resulting current flowing into the circuit. It's crucial during this measurement that the input port provides no signal (noted as '0 conductance'). By keeping these conditions, we can derive the output resistance, which is a key parameter in analyzing the amplifier's performance under feedback. This ideal condition facilitates accurate measurements and effects of feedback on the amplifier's output characteristics.
Examples & Analogies
Imagine you are using a garden hose (the output resistance) to water your plants. If you cover the end of the hose with your thumb (making the output pressure-like situation), you are creating resistance to water flow. If you try to measure how much water comes out while your thumb is blocking the end, you wouldn't get an accurate reading. This is similar to how we need to ensure the input is 'blocked' (or 0) when measuring the output resistance of the amplifier.
Non-Ideal Factors in Feedback Configuration
Chapter 3 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Now, let we consider non idealistic situation one at a time or let we introduce one by one. To start with if we consider that signal source it is having finite conductance; that means, if I consider say some finite R. So, if I consider this is finite, then whatever the current i will be having it is not same as βv, but it will be having a current division.
Detailed Explanation
In this part, we discuss the implications of non-ideal situations on the feedback configuration. Specifically, we start by considering the effect of the signal source having a finite conductance. This means that rather than all the current passing through the amplifier, some of it divides due to this finite resistance. The feedback ratio (β) must then be recalculated to account for this division, as the relationship between input voltage and output current changes. It is essential to incorporate these real-world factors to ensure accurate modeling of the amplifier's behavior.
Examples & Analogies
Think of this situation like sharing a pizza among friends. If you have a finite number of slices (finite resistance), not everyone can have the same amount (current division). Some friends (the amplifier) will get a different portion of the pizza (current) based on how the slices are distributed, thus affecting how everyone feels about the meal. Similarly, when using finite conductance, the output response of the amplifier changes based on how the input is configured.
Calculating Output Resistance with Finite Resistances
Chapter 4 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
So, let me call this is β′. So, β′v, where β′ = β ×. So, whatever the previous discussion we already have namely i = that is valid in this case also and then if we replace this v terms of β′v from that we can get i =.
Detailed Explanation
In this chunk, we derive new expressions for feedback when finite resistances are present in the circuit. By introducing a modified feedback factor β′, which adjusts the original feedback factor β based on observed conditions, we can compute the new output resistance influenced by this feedback factor. The relationship between output current and input voltage is then expressed using this new factor, illustrating how feedback is adapting to changes in circuit behavior due to non-ideal conditions.
Examples & Analogies
Consider you’re trying to calculate your total savings (output resistance) after some unexpected expenses (finite resistances). The savings you can count is reduced based on these expenses, similar to how β′ modifies the initial feedback factor β in our equations. This adjustment reflects the true state of your finances, just as β′ reflects the circuit's adjustments under those non-ideal conditions.
Final Consideration of Non-Ideal Effects
Chapter 5 of 5
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Now, if I also consider that input resistance, this is also finite. So, if I consider some finite resistance here, then we have to consider that resistance effect also.
Detailed Explanation
In this final chunk, we summarize the cumulative effects of all previous non-ideal factors. By assessing the impacts of finite input resistance along with the previously discussed effects, we begin to form a complete picture of how our feedback circuit behaves under realistic conditions. The output resistance expression incorporates all these resistances, providing a clear view of the feedback circuit’s performance in practical applications.
Examples & Analogies
Think of it like fixing a complex plumbing system where you need to account for each pipe and joint (finite resistances). Each addition impacts overall flow, just as each component in the feedback configuration affects output resistance. When all factors are considered, you can ensure the plumbing system functions efficiently, ensuring water flows smoothly just as you want your amplifier's feedback to work effectively.
Key Concepts
-
Feedback Configuration: Refers to how feedback signals are integrated into amplifier circuits to enhance performance.
-
Output Resistance: Changes induced by feedback to the output port, impacting overall circuit behavior.
-
Ideal vs Non-Ideal: Understanding the differences between ideal feedback conditions and real-world scenarios.
Examples & Applications
Using a trans-impedance amplifier in a photodiode application to convert light into voltage.
Implementation of feedback in a precision amplifier circuit to stabilize output against fluctuations.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Current flows in, voltage comes out, feedback shines where there’s doubt.
Stories
Imagine a team where every member contributes feedback to improve their project. Just like that, feedback in amplifiers adjusts output for the better!
Memory Tools
Remember C-O-M for trans-impedance: Current to Output, Maximizing.
Acronyms
F-E-E-D for Feedback Effects on Output, Enhancing Design.
Flash Cards
Glossary
- TransImpedance Amplifier
An amplifier that converts current input to voltage output.
- Feedback
A process where a portion of the output signal is returned to the input to enhance or stabilize the performance of an amplifier.
- Output Resistance
The resistance that a circuit exhibits at its output, which can change due to feedback connections.
- Shunt Feedback
A type of feedback where the feedback signal is taken from the output and returned to the input in parallel.
- Current Division
The principle by which current entering a node splits among the available parallel paths according to their resistances.
Reference links
Supplementary resources to enhance your learning experience.