61.6.2. Plan of the Lecture

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.

In this chunk, the instructor outlines the previous topics covered in the course. They mention different amplifier configurations such as Common Emitter (CE), Common Collector (CC), Common Source (CS), and Darlington pair, as well as the theory and numerical examples associated with these topics. This sets the context for the current lecture on cascode amplifiers as a continuation of their learning journey.

Imagine building a Lego set where each piece represents a different electronic circuit or amplifier. Before starting the complex structure, you ensure you have all the foundational pieces (CE, CC, etc.) built correctly. Each piece supports the next step, contributing to the final creation, just like understanding earlier topics helps comprehend the cascode amplifier.

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

Here, the instructor introduces cascode amplifiers, describing them as combinations of common emitter (CE) followed by common base (CB) configurations, and similarly for MOSFETs with common source (CS) followed by common gate (CG). This highlights the structure of the cascode amplifier and its relationship to more familiar configurations.

Think of combining two successful recipes in cooking. The CE amplifier is like a flavorful base sauce, and the CB amplifier adds an additional layer of flavor, creating a richer dish. Just as these ingredients blend to create a gourmet meal, CE and CB work together in the cascode amplifier to enhance performance.

So, I like to say that you might have observed that if we consider simply common emitter amplifier, its gain is typically quite high more than 100. On the other hand if I consider common source amplifier it is gain it is not so high. So, we must be having some alternative for particularly for MOSFET version otherwise that circuit may not be really much of an use. And this cascode amplifier is one of the configuration in a MOSFET amplifiers which is essentially helping to get the higher gain.

This section discusses the gain characteristics of common emitter (BJT) versus common source (MOSFET) amplifiers. While BJTs typically have high gains, MOSFETs do not fare as well in this regard, necessitating alternative configurations like cascode amplifiers. Cascode amplifiers are designed to improve gain, especially for MOSFET applications, making them more practical.

Consider an athlete running a race: a sprinter shines in short-distance races (akin to BJT's high gain), while a long-distance runner may excel in endurance (like MOSFETs). To compete effectively, the long-distance runner may adopt strategies (like the cascode setup) that help them gain speed and strength, similar to how cascode amplifiers enhance performance.

we made a summary that a different performance matrices of CE amplifier... So, we need to basically revisit this important property of CE and CB to motivate ourselves that combining CE and CB it is giving us a better performance.

This chunk emphasizes the importance of understanding the performance metrics of both common emitter (CE) and common base (CB) amplifiers. The instructor notes that revisiting these properties can illustrate how combining them can enhance overall performance, motivating students to examine the cascode amplifier further.

Imagine a basketball team. The key players (CE and CB) each have their strengths and weaknesses. When they work together (combine their performances), they can achieve an outcome (high gain) that is greater than any of them could achieve alone, similar to how the cascode amplifier benefits from their combined properties.

So, let us see first the CE and CE followed by CB and then cascode using BJT.

The instructor sets the agenda for the current lecture. They plan to first discuss the common emitter (CE) followed by common base (CB) configurations, leading to a detailed explanation of the cascode amplifier using BJTs. This structure helps students understand the logical flow of the lecture.

Think of this lecture as a journey. The first stop is exploring the CE and CB amplifiers, giving students foundational knowledge before heading to the ultimate destination: the cascode amplifier. Just as a trip often follows a planned route to avoid getting lost, the instructor outlines a clear path for learning.

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