95.1.2. Introduction

Dear students and participants, welcome back to our NPTEL online certification course on Analog Electronic Circuits myself Pradip Mandal from E and EC department of IIT Kharagpur. Today’s topic of discussion it is; it is continuation of feedback circuit and what we will see that the Effect of Feedback network on Frequency Response of the forward amplifier. So, if we recall the our overall plan. So, we are according to our schedule we are in week-10 and it is module-9. And at present we are system and subsystem level of electronics analog electronic circuits. And as I said that we already have started feedback system and four different configurations we have seen. And today what we will see that change of frequency response of an amplifier due to the presence of feedback network.

This introduction sets the stage for the topic of the lecture, focusing on the effect of feedback on the frequency response of amplifiers. Professor Pradip Mandal mentions that this discussion continues from previous sessions and emphasizes feedback systems in analog circuits. The importance of understanding frequency response is highlighted, particularly regarding gain, which is a critical component in amplifier performance. The context of the course structure, being in week 10 and module 9, provides a roadmap for what students have covered and what they will learn next.

Think of an amplifier like a microphone and speakers at a concert. The feedback in this case is similar to how the sound of the speakers can echo back into the microphone, altering the sound output. Understanding how feedback modifies the frequency response helps audio engineers ensure that the sound remains clear and balanced, not muffled or shrill, much like adjusting the settings on a mixer.

In general, we can say that it is valid for even other linear circuit, but our specific focus it will be on amplifier. And also the when you say frequency response, it is primarily our focus it will be on gain of the amplifier, but that is also applicable for impedance. In fact, that is applicable for with other gains also current gain, transconductance, transimpedance and so and so. So, our discussion today it is relatively generic and we will see that how the frequency response changes due to the presence of feedback circuit.

This chunk emphasizes that while the concepts discussed may apply to various linear circuits, the focus is specifically on amplifiers. The frequency response is explained as a key aspect, primarily relating to the gain of the amplifier, but also touching on other factors like impedance and different types of gains. This raises awareness that feedback can affect multiple performance metrics of an amplifier, not just gain, and sets up a more comprehensive discussion on how these relationships manifest in practical terms.

Consider a car's engine, which needs to adjust its fuel intake based on speed and load. Similarly, an amplifier adjusts its operations based on feedback regarding its frequency response, ensuring optimal performance under varying conditions, just like an engine running smoothly under different road conditions.

The concepts we will be covering today it is primarily how the locations of the poles are getting changed, in the feedback system and that is due to the location of the amplifiers poles and also the poles of the feedback network. We shall focus on the situation where the amplifier may be having one pole or maybe it is having two poles or maybe three poles. And also, we will be considering cases where feedback network may not be having any pole only the amplifier maybe having pole or maybe the amplifier as well as the feedback network may be having poles.

Here, the speaker introduces the concept of poles within the context of feedback systems, explaining that the position and number of poles influence the overall behavior of the feedback system. The speaker plans to discuss scenarios involving amplifiers with varying numbers of poles, indicating that the influence of feedback can significantly differ based on the specific setup of the amplifier and its feedback network. This sets the foundation for understanding more complex feedback behaviors in subsequent discussions.

Imagine a seesaw. Each pivot point (pole) affects how the seesaw balances when weight is applied. In an amplifier, the poles determine how feedback will influence the system's stability and performance, just as different placements of weight can affect the balance and motion of a seesaw.

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