55.1.1. Prof. Pradip Mandal

Yeah, dear students welcome back to the online certification course of Analog Electronic Circuits. Myself Pradip Mandal from E and EC Department of IIT, Kharagpur, today’s discussion it is Multi Transistor Amplifiers. So far we have discussed about different amplifier configurations, so where one transistor primarily you know single transistor it was doing the amplification and other activities. So, the transistor it was either BJT or MOS transistor and for different configurations we have seen the merits and demerits of the different configurations.

In this chunk, Professor Pradip Mandal introduces the topic of Multi-Transistor Amplifiers. He greets the students and provides context on the course, highlighting the concept of amplifiers, specifically focusing on those utilizing more than one transistor. Previously, the course covered single-transistor amplifier configurations and their advantages and disadvantages. Understanding both BJT (Bipolar Junction Transistor) and MOS (Metal-Oxide Semiconductor) configurations sets the foundation for exploring more complex circuits involving multiple transistors.

Think of single transistor amplifiers as a solo musician performing a song. They can perform well alone, but to produce a richer sound, you may want a whole band (multi-transistor amplifiers). Each band member adds their unique sounds, harmonizing together to create a more engaging performance.

Based on that merits and demerits we shall try to combine different configurations together, so that we can get overall better performance. But, before going to the overall plan let me see our alignment with our course layout. We are in week-6 and we are in between of the block level and module level. In fact, we are will be moving back and forth here. And, so, philosophically we can say there these are building blocks or they may be modules and to be precise whatever the topic we will be discussing here it is common emitter, common collector cascaded together.

In this chunk, the professor explains the motivation for integrating various amplifier configurations. The goal is to achieve superior overall performance by combining configurations that have different strengths and weaknesses. He outlines the course structure, indicating that students are currently in the process of learning about the progression and integration of concepts, specifically focused on configurations such as common emitter and common collector. These configurations will be further explored in the context of enhancing performance.

Imagine mixing different ingredients to create a dish. Some ingredients may enhance flavor while others improve texture. By combining them thoughtfully, you can create a delicious meal. Similarly, combining different amplifier configurations allows engineers to leverage unique benefits from each to create an effective solution for signal amplification.

So for each similarly the Darlington pair and so and so and for each of these configurations you may say that as they are involved more than one transistor this configurations it may be named as multi transistor amplifier. And, the purpose of that is of course, getting better performance compared to whatever we have obtained from single transistor amplifier.

This chunk describes what qualifies a circuit as a multi-transistor amplifier, specifically mentioning configurations like the Darlington pair which consists of two BJTs arranged in such a way to improve current gain. The primary focus is on achieving better overall performance through the use of multiple transistors compared to single-transistor amplifiers, both in terms of amplification effectiveness and signal integrity.

Consider a relay team in track and field. While one runner can cover a distance, a team of runners can complete it much faster by passing the baton effectively throughout the race. Similarly, multiple transistors in an amplifier can work together to 'pass the baton' of the electrical signal, enhancing overall performance.

So, let us see what is the overall plan in the next slide. The topic we will be covering today it is enlisted here. We shall start with the motivation of going for mixing different configuration together and then we basically we will summarize whatever the earlier discussion we are having. Based on that we shall see that how meaningful mixing it is useful to change the impedance and change the output impedance and maybe what is the overall circuit performance particularly when you consider for the bandwidth of the circuit.

Here, the professor outlines the agenda for the session. This includes discussing the rationale behind combining different circuit configurations. He plans to summarize previous discussions and explore how mixing configurations can help modify input and output impedances, which, in turn, impacts circuit performance and bandwidth. This provides a roadmap for understanding complex signal behaviors in multi-transistor amplifiers.

Think of a team project where everyone has different strengths. By combining those strengths, like planning and execution, the project can achieve more than if each person worked on their part alone. This is similar to how different amplifier configurations can work together to enhance overall performance.

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