94.2.1. Summary of Concepts

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 primary goal is outlined: to analyze a feedback system by determining its voltage gain, input resistance, output resistance, and output voltage when given a specific input voltage (100 mV). This sets the stage for the detailed calculations that follow.

Imagine trying to find out how efficient a pump is at pushing water through a garden hose. Just as you would measure the flow speed and resistance to understand the pump's performance, here, engineers measure the feedback system's performance to understand how well it amplifies signals.

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.

This chunk introduces an ideal feedback scenario, where the input resistance is considered infinite and the output resistance is zero. In practical terms, this means that the feedback network doesn't lose any signal when it enters and has full output capability. It's an ideal situation to simplify calculations.

Think of an ideal road with no speed limits and no obstacles. Vehicles can travel as fast as they can without any slowdowns. Similarly, an ideal feedback network operates without resistance to signal flow, thus amplifying the input fully.

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.

The feedback network allows the input resistance to increase significantly, in this case by a factor of 20 from the original input resistance of 1 kΩ to 20 kΩ. This increase is an essential feature of feedback systems as it helps in reducing the impact of external loading effects on the circuit components.

Imagine a very quiet room (1 kΩ input resistance) where a whisper is easily heard. Now, if you add soundproofing and enhance the acoustics (feedback network), even the softest sounds can be picked up, making the room feel much more sensitive (20 kΩ input resistance).

So now we obtained input resistance of the feedback system, output resistance of the feedback system and next thing is that what is the output voltage? It is very straight forward.

This chunk concludes the calculations for input and output resistance. The analysis shows how feedback networks modify a circuit’s properties, leading to a straightforward calculation for output voltage based on the previously computed gains.

Consider a public speaker whose voice is amplified through a sound system. The greater the input volume (input resistance), the more clearly their voice is projected (output voltage) to a larger audience. Here, just as the system's settings affect how loudly the speaker can be heard, the feedback circuit's parameters dictate signal amplification.

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 second case, the feedback network's parameters are altered to reflect a non-ideal scenario where both input and output resistances are finite. This presents a more realistic situation, as all systems have some active resistance, relegating ideal conditions more to theoretical discussions.

Imagine a busy street (finite resistance) where cars can travel smoothly but may encounter traffic delays. The ideal condition was like a magically perfect road. The second case illustrates real-world dynamics, showing the need for adjustments based on inherent limitations.

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