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98.1.1. Applications of Feedback in Amplifier Circuits (Part-B)
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Today, we'll explore how feedback stabilizes the trans-impedance in common emitter amplifiers. Can anyone tell me what trans-impedance is?
Is it like how much voltage we get for a certain input current?
Exactly right! Trans-impedance is defined as the relationship between the output voltage and input current. Now, how do you think negative feedback helps in stabilizing this?
Maybe it helps reduce distortion and makes the circuit respond better?
Correct! Negative feedback minimizes variations in output impedance. Let's remember this by using the acronym 'SURE' for Stabilizing, Unifying, Reducing errors!
SURE! Got it!
Good! Let’s dive deeper into the specific configurations now.
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We've established that feedback stabilizes the trans-impedance. Can anyone explain the difference between voltage-shunt and shunt-shunt configurations?
I think voltage-shunt means we're dealing with voltage feedback while shunt-shunt uses current feedback.
Exactly! Voltage-shunt feeds back voltage to control the input while shunt-shunt feeds back a fraction of the output current. Why do you think this matters?
It affects the overall gain and stability of the amplifier!
Right! Let's remember 'VIVA' - Voltage in, Voltage out - for the Voltage-Shunt feedback. Now, let’s explore input and output resistances next!
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Create a free accountNow, let's calculate input and output resistance. How can feedback impact these values?
I think it can lower the resistance, especially when something is shunted.
Yes! When the feedback network is applied, the local inputs are reduced, which is crucial for amplifier design. Can anyone provide a formula for these resistances?
I remember R_in = r/(1 + βZ') and for output, it’s R_out ≈ R_0.
Excellent recap! Remember the phrase 'IN = INt' for Input and Output Nets. Now, as we calculate values, why is it important to have proper loading effects accounted?
To avoid distortion in the output signal!
Exactly! Great job, everyone.
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Create a free accountFeedback not only stabilizes trans-impedance but also impacts the voltage gain and current gain. Can anyone explain how?
I think it normalizes the gains, so they both appear more consistent.
That's right! It helps maintain a stable A value. Let's call this phenomena 'GAIN' for 'Gains Are In Normality'. What about transconductance? How is it affected?
It's also stabilized, but might increase with negative feedback, right?
Absolutely! This could be thought of as 'accelerating the current control' which is key for effective amplification.
Overview
Short Summary
This section discusses the application of feedback in common emitter amplifier circuits, focusing on the stabilization of trans-impedance and input/output resistance.
Medium Summary
This section explores how negative feedback in common emitter amplifier circuits leads to stabilization of trans-impedance and the interactions of input and output resistances. It emphasizes the importance of feedback configuration and its components in determining circuit behavior.
Reference YouTube Videos
Key Concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
Negative Feedback: Reduces circuit gain and increases stability.
Trans-Impedance Stabilization: Ensures output voltage is predictable for given input current.
Voltage-Shunt vs. Shunt-Shunt: Different feedback configurations that impact performance.
Resistance Changes: Feedback affects both input and output resistances leading to stability.
Impact on Gains: Negative feedback maintains consistent amplifier gains.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
If a common emitter amplifier has a trans-impedance of 500 kΩ and feedback is introduced, its trans-impedance may stabilize around 50 kΩ.
Applying feedback might a voltage-shunt configuration to yield more predictable voltage outputs while managing current inputs effectively.
Memory Aids
Interactive tools to help you remember key concepts
Stories
Flash Cards
Glossary
TransImpedance
A measure of how a device converts current to voltage, defined as voltage output per unit of input current.
Negative Feedback
A process where a portion of the output is fed back to reduce the gain of the amplifier, enhancing stability.
Input Resistance
The resistance seen by the input signal, influenced by feedback configurations.
Output Resistance
The resistance at the output of the amplifier that the load experiences, also affected by feedback.
Transconductance
The relationship between change in output current to change in input voltage, often impacted by feedback.