Loading the lesson
Loading the lesson
Search AllRounder.ai
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Search the courses, subjects, tracks, games and features, or jump straight to a page.
Learn it your way
A short class with Sarah and her students. The other ways are under More.
Sign up free to listen. Transcripts are free to read.
Today, we'll explore negative feedback in amplifiers. Can anyone tell me what negative feedback does?
It helps to stabilize the amplifier's gain and performance, right?
Exactly! By applying negative feedback, we can define the trans-impedance Z as equal to A, the gain of the amplifier. Remember, Z stabilizes the circuit.
What configurations can we use for this feedback?
Good question! We typically use voltage-shunt configuration in such scenarios. This mixes output voltage with the input current. Can anyone think of why that might be important?
It allows for consistent performance under varying load conditions.
Precisely! This feedback mechanism thus enhances stability.
Recap for today: Negative feedback stabilizes gain, and we primarily use volt-shunt configurations.
Now, let’s shift to input and output resistances. Who can tell me why understanding these values is crucial?
They determine how the amplifier interacts with other components, right?
Exactly! When feedback is applied, the input resistance decreases while the output resistance is modified. Can someone remind me the relationship?
The input resistance becomes r/(1 + βZ') and the output resistance can reduce similarly.
Correct! The changes ensure we minimize loading effects. Who remembers how we approach analyzing these conditions?
We simplify and consider ideal loading scenarios to calculate proper values.
Great summary! Ensuring low loading is vital for circuit performance.
Let’s wrap our concepts around Thevenin equivalents. Why do we use them?
They make analyzing complex circuits easier by simplifying them into voltage and resistance.
Exactly! For feedback configurations, this is a crucial step. Can we reflect an example circuit into its Thevenin equivalent?
We replace the amplifier with its Thevenin voltage and resistance to analyze the load.
Right! And remember, knowing the internal Thevenin resistance is vital for calculating gain effects particularly under feedback conditions.
Remember, applying Thevenin equivalents can significantly simplify complex circuit analysis.
Now, let’s apply this knowledge to a practical example we've discussed. Who remembers our circuit parameters?
The collector current was 1 mA and the early voltage was 100V.
Good job! With these numbers, we can apply our formulas to find the feedback’s effects on Z and resistances. What do we need to calculate the equivalent resistance?
We need to ensure our R is sufficiently greater than output and input values.
Exactly! And which formula helps analyze R under feedback?
It's R = 10r based on the various conditions laid out.
Correct! Always ensure conditions are satisfied for maximum feedback efficiency!
A technique used in amplifiers to stabilize gain.
A type of amplifier arrangement focusing on input/output relationships.
A simplified model that retains essential circuit behaviors.
A method for simplifying circuits into voltage sources and resistances.
In feedback circuits, gain won't wax, it will stabilize, that's a fact.
Picture a river flowing steadily—a feedback mechanism ensures the water's calm and controlled, just like a well-tuned amplifier.
F.I.R: Feedback Influences Resistance—helps remember feedback's role.
Z.A.R = Z (trans-impedance), A (gain), R (resistance)—the three critical parameters to remember.
Term
Feedback Network
Click to flip
Term
Thevenin's Theorem
Click to flip
A measure of how much the output voltage changes in response to the input current in an amplifier.
A circuit that samples the output and mixes it with the input to control the overall output characteristics.
The resistance offered by the amplifier at its input, affecting how it interacts with preceding stages.
The resistance seen at the output of the amplifier, influencing signal delivery to the load.
A simplified representation of a complex circuit, showing a single voltage source and series resistance.
This section explores the concept of feedback in common emitter amplifier circuits and its implications for stabilizing trans-impedance and resistances.
In this section, the focus is on common emitter amplifier circuits, highlighting the significance of feedback in stabilizing trans-impedance (Z) and analyzing input/output resistances. The configurations such as voltage-shunt feedback and their resultant formulas for effective circuit behavior are discussed.
In this section, we delve into the applications of feedback in common emitter amplifier circuits, particularly aiming to stabilize the trans-impedance of the amplifier. The use of negative feedback is emphasized, allowing the trans-impedance (Z) to be defined effectively by the feedback network. Several configurations are discussed:
Additionally, we derive equations capturing how the feedback modifies both the input and output resistances. The ideal relations suggest that if implemented accurately, these results can significantly enhance the performance of amplifiers in practical scenarios. The section concludes with various parameter analyses and example calculations, aiding in the application of theory to real-world electronic circuits.