94.2. Conclusion of Feedback System

To summarize all these 4 sub-lectures, what we have discussed in this topic of feedback system. So far we have talked about basic concepts of the feedback system, there we have introduced how we define the feedback system and then we have talked about 2 basic types of feedback mechanism or feedback system namely, +ve feedback type and ‒ve feedback types feedback system.

In this part, the lecturer summarizes the main topics covered in the previous lectures about feedback systems. They talk about the foundational concepts, specifically defining what a feedback system is. Furthermore, they explain the two main types of feedback mechanisms: positive feedback and negative feedback. Positive feedback amplifies changes or deviations, while negative feedback works to stabilize the system by reducing the effects of any changes.

Consider a thermostat in a house as an example of negative feedback. When the temperature rises above a set point, the thermostat turns off the heater, preventing the space from getting too hot. This stabilizing action illustrates how negative feedback keeps a system operating within a desired range.

In the subsequent discussion, it is mostly related to ‒ve feedback system. So then, we have talked about transfer characteristic of feedback system namely, feedback system transfer characteristic A = . So also, we have talked about loop gain = ‒ βA then, desensitivity factor, D = (1 + βA).

Continuing from the introduction, the lecturer focuses predominantly on negative feedback systems. They discuss the characteristics of these systems in terms of their performance metrics like transfer characteristics (how input signals are transformed to output), loop gain (which indicates how much signal is fed back into the system), and the desensitivity factor (which measures how the system's characteristics are stabilized by feedback). These metrics are essential for understanding how feedback impacts system stability and performance.

Think of a car’s cruise control as a feedback system. When the car goes uphill and slows down, the cruise control detects this (loop gain), and it provides more fuel to maintain speed. If the cruise control system were too sensitive (high desensitivity), any small change in speed would create a lot of adjustments, leading to an unstable ride.

Then we have talked about 4 basic configurations which normally it is common in electronic circuits and we have discussed about their characteristic. So these are the enlisted 4 basic configurations we have discussed about how the gain it is getting changed. And also we have talked about how the input resistance and output resistance of the system it is getting changed by the desensitization factor.

The lecturer highlights four fundamental configurations commonly found in electronic circuits using feedback. They emphasize how these configurations alter the overall gain of the system and how factors such as input resistance (the resistance seen by the source) and output resistance (the resistance seen by the load) can be modified by the desensitization factor, which ultimately affects performance and stability.

Consider balancing on a seesaw with friends. If one friend is significantly heavier (implying a high gain), it's harder to balance (input/output resistance). However, if you each adjust your positions evenly (adjusting configurations), it becomes easier to find a stable position, mirroring how feedback can stabilize a circuit.

And then we have discussed about 2 numerical examples associated with 2 feedback configure different types of configuration starting with ideal situation and then also we have moved to non-ideal situation.

The final part of the discussion reviews two numerical examples that illustrate the application of feedback systems in both ideal and non-ideal scenarios. This helps to concretely demonstrate how feedback systems operate in practice, illustrating the theoretical concepts discussed previously with practical calculations and real-world functionality.

Imagine learning to balance a bicycle. In an ideal situation, if you have perfect balance, you maintain a straight line effortlessly. In a non-ideal situation, you might wobble. By applying some feedback (like steering corrections), you can achieve a straighter path, just like in electrical circuits where feedback helps correct for imperfections in real-world applications.

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