94.1. Feedback System (Part- E)

So here we do have numerical example and what is our objective here? It is that we need to find the voltage gain of the feedback system, input resistance, output resistance of the feedback system and the output voltage for an input voltage or the signal voltage of 100 mV.

In this section, the main goal is to calculate several parameters of a feedback system. Specifically, it aims to find the voltage gain, input resistance, output resistance, and output voltage when a signal of 100 mV is applied. These calculations are part of understanding how feedback affects the behavior of electronic circuits.

Think of the feedback system like a thermostat in your home. When the temperature dips below a certain point, the thermostat kicks in and starts the heater. Similarly, in an electronic feedback system, the output is adjusted based on the input (in this case, the 100 mV signal) to produce a stable and desired output.

And the parameters of the feedback systems are given here: input resistance and output resistance of the forward amplifier and the gain of the forward amplifier it is 200 feedback network, the feedback factor it is 0.095.

This chunk outlines the essential parameters needed for the calculations: the gain of the forward amplifier is 200, indicating how much the amplifier increases the input signal; the feedback factor, which is 0.095, relates to how much of the output gets fed back into the system. The input and output resistances are crucial because they affect how the amplifier interacts with other components in the circuit.

Imagine a factory assembly line where 200 products are made but only 9.5 of those products are checked for quality before they're sent back into the line. The gain of 200 is like the production rate, and the feedback factor is the quality control check that influences the entire process.

So to start with, let me consider this relatively simpler case, case-1 where we consider ideal feedback network having the input resistance it is infinite and its output resistance on the other hand it is 0 as we are generating voltage.

In this first case, we consider an ideal feedback network which simplifies our calculations. An infinite input resistance means that it won't draw any current from the signal source, making the circuit more predictable. On the other hand, a zero output resistance means the system can provide high voltage without dropping voltage across itself.

Picture a perfect sponge that can absorb unlimited water without changing the water flow. The sponge represents our infinite input resistance; it absorbs information without affecting the source. Meanwhile, think of a hose with no restrictions - it allows water to flow freely, akin to the zero output resistance that delivers maximum voltage to the output.

So the gain of the feedback system it is 10. Now, to find the value of the input resistance R .

The gain of 10 indicates that the output voltage is ten times greater than the input voltage. For instance, if we input 100 mV, we would expect 1 V as output (100 mV multiplied by the gain of 10). We then focus on calculating the input resistance, showing how feedback can modify the amplifier's characteristics.

Consider a magnifying glass: it doesn't just make things look bigger; it also has its own characteristics, like how much light it can gather. Similarly, feedback in a circuit changes how the original input signal is amplified while also affecting other properties like resistance.

So note that just by this feedback network the input resistance it is getting increased by a factor of 20 which means that if the main amplifier input resistance it was 1 k, the feedback system input resistance it is becoming 20 k.

This portion emphasizes the effect of feedback on input resistance. The input resistance increases significantly due to feedback, going from 1 kΩ to 20 kΩ. This increase means the feedback network makes it easier to connect other components to the amplifier without affecting the signal.

Think of this as a crowd at a concert. When more people join in and support the music, the noise or input resistance becomes larger, allowing more sounds to be amplified without drowning out the main performance.

So the shunt connection it is reducing the resistance which means that the output resistance it will be = = 200 Ω.

In this part, it is shown that the output resistance decreases to 200 Ω because of the shunt configuration used in the feedback network. This is beneficial for the system, as lower output resistance can improve power transfer to the load.

Imagine you’re at a concert trying to push through a crowd, but instead of everyone blocking you, some move aside to let you pass. The less resistance allows you to get through easily, just as a lower output resistance makes it easier for the circuit to deliver power to the connected component.

So the output voltage v it is 10v . So that is giving us 10 × 100 mV = 1 V.

Here, we calculate the output voltage based on the previously determined gain. If we input 100 mV and the gain is 10, the output will be 1 V. This simple calculation encapsulates the essence of how feedback systems increase signal strength.

Imagine a party where one person’s excitement gets everyone else enthusiastic – the energy grows exponentially. Just as that excitement reflects back in an amplified way, our feedback system causes the output voltage to amplify based on the input.

Now if I consider the 2nd case, I should not say it is ideal. So this part may be ideal, but with finite resistance.

In this chunk, the transition is made to a second case where feedback is non-ideal. Differences from the first case include finite input and output resistances, which introduce complexities in calculations and expected outputs.

Think about ordering food online versus directly at a restaurant. Online, you are limited by the selections offered; you might have to deal with delays. Similarly, non-ideal conditions introduce limits that we have to account for in calculations.

So we need to be careful that A it is giving us 200, but A′ it is different.

This emphasizes the careful distinction between the ideal and actual gain calculations. The presence of load changes the gain we expect from what the forward amplifier states, necessitating a correction using load factors.

Think of an athlete like a runner who can sprint at full speed in a race alone but slows down considerably when carrying extra weight. Similarly, in an electronic circuit, adding load impacts the performance of the system, changing expected behavior.

So here we do have here it is . In fact, again I have done this calculation.

This segment encapsulates the calculations to deduce the changes in parameters based on new conditions and how feedback alters not just performance but also the internal characteristics like gain and resistance. Detailed calculations are performed to derive new values.

Think of recalibrating the settings on a machine after switching it to a different task. Just as those recalibrations affect the output, so too do the calculations for electronic systems when conditions change.

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