61.6.1. Introduction

Dear, students welcome back to our NPTEL online certification course on Analog Electronic Circuits, myself Pradip Mandal from E and ECE department of IIT Kharagpur. And today’s topic of discussion, it is Multi-Transistor Amplifiers in fact, this is continuation of our previous discussion.

In this introduction, the instructor welcomes students back to the course and highlights the focus of today's lecture, which is on Multi-Transistor Amplifiers. This indicates a continuation from previous lessons and sets the stage for more complex discussions ahead.

Think of this course as a progressive journey through a series of interconnected topics in electronics, much like how a chef builds a meal ingredient by ingredient, layering flavors to create a complex final dish. Each class builds on the previous ones.

Now the plan overall plan if you see according to our weekly plan so far we have covered CE – CC; CS - CD and CC - CC; Darlington pair etcetera both theory as well as numerical examples.

The instructor outlines the weekly course plan, mentioning specific amplifier configurations that have been covered in previous lectures. This includes different classes of amplifiers such as Common Emitter (CE), Common Collector (CC), Common Source (CS), and others, suggesting a comprehensive grounding in foundational material before moving to more advanced topics.

Consider this structured course like a comprehensive course on cooking. First, students learn basic techniques (like chopping and frying) before moving on to more advanced dishes that require the mastery of those techniques (such as a complex multi-layered cake).

And we are going to discuss about Cascode Amplifiers which are essentially I should say CE this should be CE, CE followed by CB and CS followed by CG.

Here, the lecturer introduces Cascode Amplifiers, explaining their structure as combinations of different amplifier configurations (CE followed by CB among them). This lays down the basis for understanding how these configurations work together to improve performance in amplification.

Imagine building a rocket where different stages represent various amplifier configurations. Each stage has a specific function and when stacked correctly, they work together effectively to accomplish the launch (or achieve high amplification).

So, I should say this is combination of common emitter amplifier with common base. So, this is BJT version and this one is a MOS version common source followed by common gate.

The instructor explains that Cascode Amplifiers can be implemented using both BJT (Bipolar Junction Transistor) and MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) technologies. This highlights the versatility of the Cascode configuration in improving gain and bandwidth in different types of amplifiers.

Think of this amplifier setup like a multi-part machine designed for efficiency, where different parts (in this case, differing transistor types) work together to optimize performance, just as different components in a car engine enhance overall horsepower.

And this cascode amplifier is one of the configuration in a MOSFET amplifiers which is essentially helping to get the higher gain.

The text emphasizes that Cascode Amplifiers are particularly significant in MOSFET design, as they can achieve higher gains compared to other configurations. This indicates their practical applications in many electronic circuits where amplification is critical.

Imagine a ladder that allows you to reach higher shelves in a library. Just as the ladder provides extra height to access valuable books (here represented by higher gain), the cascode configuration enhances the amplification abilities of your circuit.

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