52.1.3. Indian Institute of Technology, Kharagpur

Welcome back after the short break. What we are discussing is Common Base Amplifier and we will be going for Common Gate amplifier, but before going I have another example based on the common base where we are talking about practical circuit of this base bias.

In this chunk, the speaker introduces the topic of discussion: the Common Base Amplifier. After a break, they indicate that they will explore practical examples of how this type of amplifier operates, particularly focusing on the biasing arrangement which is crucial for ensuring that the transistor operates effectively in real applications.

Think of the Common Base Amplifier as a kitchen where the appliances are the components of the circuit. Just like how a well-arranged kitchen layout allows for better cooking (circuit operation), a proper biasing circuit helps the amplifier perform effectively in real-world scenarios.

Instead of having you know ideal separate voltage source here along with the Thevenin equivalent resistance R, practical circuit wise we may have only one supply voltage and from that we need to generate whatever the voltage we like to generate here.

This chunk discusses the importance of practical bias arrangements in amplifiers. Rather than relying on ideal, separate voltage sources, the discussion emphasizes generating the necessary voltages using a single supply voltage, demonstrating the practical aspects of circuit design.

Imagine trying to cook a meal using multiple individual ingredients stored across different spots in your kitchen. It might be simpler and more efficient to only use what you have on hand in one cabinet (the single supply voltage) instead of going back and forth to collect each ingredient (ideal sources).

Let us try to see the operating point of the transistor by considering R, R, and so on. Now, in this case V also I have changed. So, instead of 10 V it is 12 V and R and R both are 100 kΩ.

In this chunk, the speaker explains how to determine the operating point of the Common Base Amplifier's transistor using specific resistors and voltages. They discuss changing a voltage from 10 V to 12 V and the significance of using standard resistor values (100 kΩ) in establishing the operating point.

Think of the operating point like finding the perfect temperature for your oven. If you move from 10 degrees to 12 degrees (the voltage change), you need to consider the right settings (resistors) to ensure your dish cooks properly without burning or undercooking.

And then at the emitter DC wise we have R here and it is 10.306 kΩ and the current flow. So, we are expecting that there will be a current flow and let me call this current is I.

This chunk elaborates on the interactions within the circuit, particularly focusing on the role of the emitter resistor (10.306 kΩ) and how it influences the current flow through the transistor, which is essential in ensuring the amplifier works properly.

Imagine a water pipe where the emitter resistor is a narrow section of the pipe. The flow of water (current) must pass through this narrow section, greatly affecting how much water can actually get through, similar to how the resistor dictates the current in the circuit.

Once we obtain these small signal parameters, then rest of the things yourself can do namely you can calculate what will be the input impedance and so.

This part of the lecture introduces the concept of small signal parameters and their importance in amplifier design. After calculating these parameters, students are expected to determine the input impedance, a critical factor in understanding how the amplifier will perform with various inputs.

Think of small signal parameters as the specific ingredients (like spices) that enhance the overall flavor of a dish (the amplifier’s performance). Understanding them helps in creating a well-tasting meal, just as knowing the parameters leads to a well-performing amplifier.

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