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Learn it your way
A short class with Sarah and her students. The other ways are under More.
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Let's start by discussing what a feedback system is. Could someone tell me how we define it?
I think a feedback system is one where the output is fed back into the input to control its behavior.
Exactly, Student_1! Feedback systems help regulate the output. Now, can anyone tell me about the types of feedback?
There are two types: positive feedback, which amplifies changes, and negative feedback, which stabilizes the system.
Great insights! Remember, negative feedback generally improves stability and reduces gain. Let's move on to what we will calculate today.
Now, let's examine an ideal feedback system. Who can remind us of its characteristics?
In an ideal feedback system, the input resistance is infinite, and the output resistance is zero.
Correct, Student_3! These characteristics will affect how we compute the voltage gain. Let's calculate the voltage gain using the formula: A' = A / (1 + βA). What values do we have for A and β?
We have A = 200 and β = 0.095.
Right! Plugging those in, what do we get for the voltage gain?
It looks like the voltage gain A' becomes 10.
Exactly. Excellent work, everyone! This shows how negative feedback can stabilize the system. Let's explore how this impacts other metrics!
Next, let's calculate the input resistance, R_in of the feedback system. Can someone tell me how we do that?
We multiply the original input resistance by the desensitization factor, right?
Yes! If R_in is 1kΩ for the forward amplifier, and we have a desensitization factor of 20, what's the new input resistance?
That would be 20kΩ!
Well done! Now, who can tell me about calculating the output resistance R_out?
For output resistance in a feedback system, we reduce the output resistance due to the feedback.
That's right! So, if our output resistance is 200Ω in the feedback system, how does it change?
It remains at 200Ω due to the influence of shunt configurations!
Exactly! Great work! Let's summarize what we've learned.
Let’s wrap up by calculating the output voltage based on our previous findings. We have an input voltage, V_in of 100mV. What's the output voltage with our voltage gain A'?
Since the gain is 10, the output voltage would be 10 times the input voltage, which makes it 1V.
Excellent! This is how we find the output voltage in the feedback system! What does this say about our feedback system’s ability to amplify signals?
It indicates that we can enhance weak signals significantly using feedback!
Spot on! And that concludes our session on feedback systems. Any questions?
The relationship of input voltage to output voltage, indicating amplification.
Resistance encountered by the input signal, influencing system performance.
Resistance presented at output, impacting the efficiency of signal transfer.
The influence feedback has on the amplifying characteristics, affecting both gain and resistance.
With a forward amplifier gain (A) of 200 and a feedback factor (β) of 0.095, the voltage gain (A') calculates to 10, while the increased input resistance reaches 20kΩ.
Using ideal and non-ideal feedback characteristics, the output close to expectations reveals how calculations vary with altered parameters.
To get the gain, just multiply, input wattage to output, let it fly!
Imagine a classroom where every student's voice (the input) is amplified by a microphone (the feedback system); the louder the input, the more everyone hears (the output).
Gains Increase – G for Gain, I for Input – remember both together to find output functions.
GIRL: Gain, Input, Resistance, Load – remember it to understand the interplay of circuit configurations!
Term
Input Resistance
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Term
Output Voltage
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A system where output is routed back to input to influence behavior.
The ratio of output voltage to input voltage in a feedback system.
Resistance faced by the input signal in a feedback system.
Resistance seen at the output of a feedback system.
A factor showing how feedback changes characteristics of the system.
This section discusses calculating voltage gain, input resistance, output resistance, and output voltage of a feedback system using numerical examples.
The section illustrates how to determine the voltage gain, input resistance, and output resistance of feedback systems through a detailed numerical example. It covers both ideal and non-ideal feedback scenarios, highlighting the importance of various parameters in the amplification process.
In this section, we focus on calculating key parameters of a feedback system, including voltage gain, input resistance, output resistance, and output voltage based on given amplifier and feedback characteristics. We examine two cases: an ideal feedback network characterized by infinite input resistance and zero output resistance, and a non-ideal feedback network featuring finite input and output resistances. The numerical example begins with specified values such as the forward amplifier gain, feedback factor, and input/output resistances, guiding the reader through the detailed computations necessary to derive significant metrics of the system. We learn that the feedback mechanism can considerably influence the overall characteristics of the system, positively impacting input resistance while typically reducing output resistance. Through careful calculations and re-evaluation of different scenarios, we develop a comprehensive understanding of how feedback applies in electronic circuits.