18.1.1. Introduction

So, dear students welcome back to this course on Analog Electronic Circuits. Myself Pradip Mandal from IIT Kharagpur, I am associated with the Department of E and ECE. Today's topic for this course is Linearization of Non-Linear Circuit Containing BJT.

In this chunk, the speaker introduces themselves and welcomes students back to the course on Analog Electronic Circuits. They specify the topic of the lecture, which focuses on linearization techniques applied to non-linear circuits that include BJTs (Bipolar Junction Transistors). This sets the stage for the topic of discussion and indicates what students can expect to learn in this session.

Think of this introduction as the opening of a movie where the director (the instructor) lays out the theme (the topic on linearization) and introduces the actors (the students). Just as a movie sets the mood for its plot, this introduction outlines the learning journey ahead.

Before, I discuss about the subtopics let me see what is our position so far; as we are mentioning that this is our main flow, from component to building blocks and so and so. And, at present in this week we are the building blocks namely, the basic building blocks and in this week we have covered the analysis of simple non-linear circuits.

The speaker reflects on the learning journey of the students, mentioning that the current focus is on building blocks of circuits. They emphasize that previously covered topics include the analysis of basic non-linear circuits, indicating that students are progressing in their understanding and laying a strong foundation for more advanced topics related to BJTs and linearization.

Consider this like a building construction project. Before you can add walls and a roof, you need to lay a solid foundation. The speaker is helping students understand that prior topics are the foundation that supports the advanced discussions that will take place, like linearization.

Today, we are going to start with linearization of input or output transfer characteristic of non-linear circuit containing transistors and this linearization it will be with respect to operating point.

This chunk details the specific focus of today's session: the linearization of input or output transfer characteristics of non-linear circuits with transistors. It explains that the concept of linearization will be examined in relation to the operating point of the circuit, which is essential for understanding how the circuit behaves under different conditions.

Imagine taking a close-up photo of a flower. In doing so, you may need to adjust your focus to get a clear image. Similarly, in electronics, linearization helps us to adjust our view of the circuit’s behavior, so we can clearly see how a small change in input leads to a predictable change in output.

So, then we will also see the notion of small signal equivalent circuit. Then from that we can see that a different model of the transistors namely small signal model of transistors.

In this part, the speaker introduces the concept of small signal equivalent circuits. These are simplified models used in circuit analysis that help engineers understand how non-linear circuits can be approximated as linear over small signal variations. This is particularly useful for analyzing circuits with transistors like BJTs, allowing for easier calculations of circuit responses.

Think of a small signal equivalent circuit like a simplified map of a city that highlights only the main roads and landmarks, ignoring minor details. While the full city may be complex with many routes, the map allows a traveler to navigate effectively and quickly, similarly to how small signal models simplify complex circuit behavior for analysis.

So, basically when we say a linearization of non-linear circuit we are primarily focusing the narrow range of the input or output transfer characteristic.

The speaker emphasizes that linearization involves concentrating on a narrow range of behavior in a non-linear circuit's input-output characteristics. By focusing on a limited range, engineers can apply linear approximations, making it easier to predict circuit behavior without being misled by the complexities of the entire non-linear characteristics.

Imagine if you were trying to understand a steep hill by examining only a small, flat section at the base. Although the hill is steep and complex, analyzing the flat area would give you a clearer understanding of how to ascend. Similarly, by linearizing, engineers can understand complex circuit behaviors more simply.

So, we will see that how the small signal models are getting evolved and what is its usage of the small signal equivalent circuits for some practical circuit.

In this section, the speaker highlights that future classes will expand on small signal models, including their evolution and practical applications. This underscores the importance of understanding both theoretical concepts and real-world applications to enhance students' grasp of electronic circuit design and analysis.

Think of a chef who learns new techniques through practice and experimentation in their kitchen. Similarly, in future classes, the speaker aims to equip students with both the theory and the practical skills necessary to apply small signal models effectively in real-world electronic circuits.

--