97.1.1. Introduction

Dear participants, so, welcome back to our online certification course on Analog Electronic Circuit. Myself Pradip Mandal from E and EC department of IIT Kharagpur. Today’s topic of discussion it is Feedback; it is rather a continuation of the feedback system. Specifically, we are going to talk about the Application of Feedback circuit in amplifier.

In this introductory section, Professor Pradip Mandal welcomes participants back to the course on Analog Electronic Circuits. The focus today is on feedback, a continuation of the previous discussions about feedback systems. Specifically, the application of feedback in amplifier circuits is highlighted, indicating that both transistor-level and operational amplifier (op-amp) circuits will be covered in the lecture. This sets the stage for understanding how feedback can enhance amplifier performance.

Imagine you’re at a concert where the sound is booming, but with some parts being too loud while others are too quiet. A sound engineer adjusts the speakers' output in real-time to balance the sound evenly across the venue, just like feedback circuits help balance and improve amplifier performance.

So, the concept, so, we are planning to cover today it is listed here. We shall see how we can deploy or how do we decide different feedback configuration in BJT circuits. We will be talking about specifically three different configurations: voltage sampling and shunt feedback, current sampling and series mixing, and voltage series feedback.

In this chunk, the focus shifts to specific feedback configurations relevant to BJT circuits. Professor Mandal outlines three key configurations: voltage sampling with shunt feedback, current sampling with series mixing, and voltage series feedback. The importance of understanding these configurations lies in their practical application in amplifiers, guiding how feedback can be effectively implemented for desired results.

Consider a handyman looking for the right tools to fix different parts of your home. Each configuration is like a specific tool—each serves a unique purpose and is chosen based on the task at hand, just like engineers select feedback configurations based on specific amplifier requirements.

So, here we have four different configurations; namely voltage-shunt, current-shunt, voltage-series and current-series or shunt-shunt, series-shunt and then shunt-series and series-series.

This section summarizes four primary configurations for feedback systems: voltage-shunt, current-shunt, voltage-series, and current-series. Each of these configurations has unique characteristics that determine their input and output signal types, affecting the overall amplifier's performance. Understanding these configurations is crucial for anyone working with feedback in electronic circuits.

Think of a family of transmitters that send signals to each other in different channels. Each type of channel serves a specific need, just like these feedback configurations channel the amplifier's input and output signals to achieve optimal performance.

Depending on these configurations, we can say what type of signals we do have at the input. And also we can see what type of signals we have at the output of the system.

This part explains how different feedback configurations influence both the input and output signals of amplifiers. By analyzing the type of feedback used, engineers can predict changes in amplifier gain, making it vital to understand how these configurations alter system behavior. This knowledge is key to designing effective electronic circuits.

Imagine a filmmaker using different camera angles and lenses to capture scenes from a movie. Each angle and lens alters the viewer's perception—similarly, each feedback configuration changes how the amplifier interprets and outputs signals, shaping the overall performance.

When we want to stabilize a specific parameter, we should select the corresponding configuration based on the feedback network, while being aware of input and output resistances.

In this segment, Professor Mandal emphasizes the importance of selecting the correct feedback configuration to stabilize desired parameters, such as input and output resistances. Recognizing how resistances may change as a result of feedback is critical for designing circuits that meet specific requirements and minimize overall performance degradation.

Choosing a specific feedback configuration is like a chef deciding which seasoning to use while cooking. The right seasoning emphasizes flavors in the dish, while using the wrong one can overpower or spoil the meal. Similarly, selecting the correct feedback configuration enhances amplifier performance.

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