16.3. Introduction

Dear students welcome back to this Analog Electronics Circuit. Myself Pradip Mandal from IIT Kharagpur, I am associated with the E and ECE Department of the Institute. We are going through the second module, a continuation of our previous work focusing on the analysis of simple non-linear circuits containing BJT and MOSFET.

The course is being conducted by Professor Pradip Mandal from IIT Kharagpur, focusing on Analog Electronics Circuit. The course aims to explore the analysis of non-linear circuits, specifically looking at two types of transistors: BJT (Bipolar Junction Transistor) and MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor). The current module is a continuation from the previous one that dealt with BJT, and now the focus will shift to MOSFETs, highlighting the differences in their operation and analysis.

Think of it like learning to drive two different types of cars. In one training module, you learned to drive a sedan (BJT), and now you're moving to learn how to handle an SUV (MOSFET). While both have wheels and engines, the way they respond to steering inputs and manage power differs significantly, just like the analysis of BJTs vs. MOSFETs.

Today we will be going to similar kinds of analysis, but containing MOSFET. First, we will cover the basic circuit configuration. This will involve one transistor, and through two examples, we will find circuit solutions, including circuit current and voltage. We will cover the common source amplifier, observing the output variations when the input changes.

The primary objective of today's class is to learn how to analyze circuits that use MOSFETs, similar to what was done previously with BJTs. The focus will be on understanding the basic configuration of these circuits, specifically a common source amplifier, which has a common source point for both input and output. By conducting two examples, we will derive the circuit's current and voltage characteristics and explore how changes in the input affect the output signal.

Imagine you are trying to tune an audio speaker. When you turn the volume up (input change), the sound becomes louder (output change). In this lesson, we'll learn how small changes in the inputs to a MOSFET circuit result in changes in the output signal, similar to how volume control affects the sound from speakers.

We will examine what kind of output we expect when the input of the common source configuration is varied. Essentially, we are looking for the input-output transfer characteristics of the circuit.

This part of the lesson will focus on the concept of signal amplification within a MOSFET circuit. Specifically, we will analyze how varying the input signal results in a corresponding change in the output. This relationship is described as the input-output transfer characteristic. Understanding this concept is crucial for designing circuits that effectively amplify signals, which is a key function of many electronic devices.

Consider a microphone connected to a loudspeaker. When you speak into the microphone (input), it picks up your voice and amplifies it through the speaker (output). The process we are studying is analogous to this: we will observe how input signals can be manipulated to achieve amplified outputs using a MOSFET circuit.

If time permits, we will cover some numerical examples in detail. Otherwise, hints can be given for students to work on these problems.

The final part of today's class will involve practical numerical examples that apply the theoretical concepts discussed earlier. If time allows, we will work through these examples step-by-step, providing a deeper understanding of the calculations and methodologies used in analyzing MOSFET circuits. If not, students will receive guidance on how to approach these problems on their own.

Think of this segment as a cooking class where you’ve learned the recipe (theory), and now you're going to apply it in the kitchen (numerical examples). Whether we cook together today or I give you the recipe to try at home later, the goal is to practice and reinforce your understanding through hands-on experience.

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