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A short class with Sarah and her students. The other ways are under More.
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Today we're going to discuss feedback systems in analog electronic circuits. Can anyone share what feedback means in this context?
Is it when the output of a system is fed back into the input?
Exactly! That's a great definition. Feedback is crucial as it helps stabilize and adjust the system's performance. There are primarily two types of feedback: positive and negative. Can anyone tell me how they differ?
Negative feedback reduces the output, like controlling a thermostat?
Yes! And positive feedback increases the output, often pushing the system towards instability or oscillation. Remember, negative feedback is generally used for stabilization.
So negative feedback is more beneficial usually?
Correct! It usually enhances stability and performance.
To summarize, feedback is essential for controlling the behavior of electronic circuits. We'll explore calculations related to voltages and resistances next.
Let’s start calculating the voltage gain for an ideal feedback system. Who can tell me the formula for voltage gain in feedback systems?
Is it A' = A / (1 + βA)?
Exactly right! For our case with A = 200 and β = 0.095, let’s do the math together. What do we get for A'?
If we substitute, it should be A' = 200 / (1 + 200 * 0.095). It simplifies to 10!
That's correct! You can see how feedback significantly reduces the gain. What about input resistance?
Isn’t it affected by the desensitization factor? The input resistance should increase?
Yes, right! For a forward amplifier with an input resistance of 1 kΩ, it becomes 20 kΩ. So, what do we conclude about our ideal system's performance?
The feedback allows us to have higher input resistance and lower output resistance!
Great summary! Remember, this ideal case sets a benchmark for understanding how feedback can enhance circuit performance.
Now, let’s discuss non-ideal feedback systems. How does introducing finite resistance change our previous results?
I think it would make the input resistance lower?
That’s right! With finite input resistance, our calculations adjust. Can anyone explain how we'd calculate the new values?
We have to consider both loading effects and the new resistances, right?
Yes! The loading factor is essential. If the input resistance is 200 Ω, how does that affect the gain?
I think A' would be less than before because it would see less input voltage.
Exactly! Thus, our new gain appears to be much lower. Effective changes often require careful accounting of all resistances involved. What was the resultant output voltage from a 100 mV input?
I think it becomes about 655.73 mV.
Well done! Understanding these changes is vital in real-world applications, as non-ideal feedback is common.
What have we learned about feedback systems? Can someone summarize key points?
We learned the difference between ideal and non-ideal feedback systems and how it affects gain and resistance.
Exactly! What applications do you think this knowledge helps with?
Designing stable amplifiers and understanding how to optimize their performance!
Great! Feedback systems are crucial in a myriad of electronic designs. With real applications requiring us to handle both conditions, professionals need to be adept at these calculations.
This was enlightening! It clarifies why we need to design circuits carefully.
Yes! And always keep practicing those calculations. Let’s keep feedback considerations in mind for our future circuit designs!
In an ideal feedback system with a forward gain of 200 and a feedback factor of 0.095, the output gain is calculated as A' = 10.
In a non-ideal case where the input resistance is 200 ohms and output resistance is 1k ohms, the modified voltage output becomes 655.73mV from an initial 100mV signal.
Feedback helps circuits grow, make signals strong, keep distortions low.
Imagine a teacher giving feedback to a student. The student improves each test, just like a feedback system enhances performance.
FIVE: F - Feedback, I - Input, V - Voltage, E - Energy - always remember the components of feedback systems.
GAIN - G - Gain, A - Amplifier, I - Input, N - Network.
Term
Feedback Definition
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Term
Voltage Gain (A')
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The proportion of the output that is fed back into the input of the system.
The factor by which feedback amplifies the input resistance and alters the output resistance.
The resistance seen by the load connected to the output of a circuit.
This section discusses key findings on the feedback system within analog electronic circuits, including calculations of voltage gain, input and output resistance, and output voltage.
The section provides in-depth analysis and calculations related to the feedback system in analog electronic circuits. Key findings involve understanding the effects of different configurations on voltage gain, input resistance, and output resistance, illustrating how system parameters change under ideal and non-ideal conditions.
In this section, we explore the impact of feedback systems in analog electronic circuits, emphasizing the calculations involved in determining voltage gain, input resistance, and output resistance. We first demonstrate these calculations under ideal conditions, where the feedback network is assumed to have infinite input resistance and zero output resistance, significantly enhancing the system's performance.
The first case illustrates an ideal feedback system with a forward amplifier gain of 200 and a feedback factor of 0.095, leading to a feedback system gain of 10 (calculated as A' = A / (1 + βA)). This example shows how the input resistance increases by a factor of 20, while the output resistance decreases, resulting in a 1V output voltage from a 100mV input signal.
Transitioning to a non-ideal scenario, we analyze the impact of finite resistances in the input and output stages. This analysis highlights how the parameters diminish the overall voltage gain and alter resistance values, leading to more complex calculations. For instance, using a loading factor calculation, we derive a modified gain and adjusted resistances accordingly, demonstrating that the output voltage drops to approximately 655.73mV under these conditions.
The insights gained from this section are foundational for understanding the application of feedback in electronic systems and underscore the importance of analyzing both ideal and non-ideal behaviors to predict system performance accurately.