64.1.6. Part B

So, far what we have discussed that the advantage of cascode amplifier with respect to standard CE amplifier and namely what you have seen is that in case if you are retaining this passive element for both the cases, then gain wise we do not get much advantage. But then what we have seen that in case if we have the input resistance and the source resistance together forming a significant low frequency pole due to this large value of the C , in then we have seen that the cascode amplifier it is giving some advantage.

In this section, the instructor highlights the benefits of using a cascode amplifier compared to a standard common-emitter (CE) amplifier. While initially, it appears that there isn't much advantage in terms of gain when using passive elements, the cascode amplifier provides significant enhancements in scenarios where the input resistance and source resistance create a low-frequency pole. This behavior is largely attributed to the larger capacitance involved, which allows the cascode design to improve bandwidth and signal integrity.

Imagine you're trying to listen to music on your phone in a crowded area. A regular speaker (CE amplifier) might not be loud enough to compete with the noise around. However, using headphones (cascode amplifier) helps you to tune into the music clearly without interference from surrounding sounds, just as the cascode amplifier effectively manages signals in electronic circuits.

In fact, cascode amplifier it is having two types of advantages; one is extending the bandwidth as we just now we have discussed particularly in presence of significantly large value of the source resistance, the other advantage which is commonly used is that the increasing the gain drastically.

The cascode amplifier offers two primary advantages: It extends the bandwidth of the signal and increases the gain significantly. By managing the source resistance appropriately, the cascode design allows for better transmission of signals over varying frequencies. The concept that a higher output resistance in a cascode configuration can lead to improved gain is crucial for designing high-performance amplifiers.

Think of a long road with many speed bumps. If the bumps (source resistance) manage the speed too much, you won't get to your destination efficiently. However, if you were to switch to a smoother road (cascode technology), you could travel faster while getting more distance covered, thus achieving better overall performance, similar to how the cascode amplifier enhances both bandwidth and gain.

So, to demonstrate the capability of the cascode amplifier to increase the gain first of all let we consider a different situation instead of having this R if you put some active circuit there, probably then the advantage of the cascode amplifier particularly for enhancing the gain it will be quite prominent.

The instructor now sets up a numerical example to illustrate the cascode amplifier's capacity for increased gain. By substituting a resistance with an active circuit, the unique benefits of the cascode configuration become more apparent. This approach allows for significantly higher gains than seen with static resistive configurations, thus demonstrating improved performance in applications requiring amplification.

Imagine trying to amplify sound at a concert using different methods. A regular speaker system might not be powerful enough (using a resistor), but by integrating a professional sound mixing board (active circuit), the sound can be adjusted and amplified effectively to reach every corner of the venue, just like enhancing signal strength in a circuit.

On the other hand if I consider practical circuit and let me use the analysis slight analysis here. If I consider the resistance of this part in fact, this resistance equivalently you can see the value of this resistance it will be roughly g r r . If I ignore say or if I consider this node it is connected to ground.

In this part, the instructor discusses the practicalities of the circuit and how to evaluate the output voltage based on the equivalent resistance. By analyzing the circuit in terms of transistor parameters and their relationships, students learn how to derive values that inform them of the circuit's behavior under different conditions, such as the influence of parallel resistance on output voltage.

This analysis is similar to calculating the output of a power supply system. If you have several power sources connected (transistors), understanding how much power each contributes and how they are configured (resistances) will allow you to predict how much total power you will get in the end, enabling effective energy management.

In fact, this is the reason why we have picked up this 10 MΩ it is not only feasible, but it is also a meaningful value and if I consider the practical value of this resistance, then what about the little current it will be flowing here that current we will also be consumed by the equivalent resistance there.

The choice of 10 MΩ resistance is explained to be practical and beneficial for achieving the desired performance in the circuit. The instructor explains that the slight current that flows through it will interact with the equivalent resistances, affecting voltage levels. Understanding how resistances impact current and voltage in a circuit is key to designing effective amplifiers.

Think about water flowing through various pipes (resistances) in a plumbing system. The larger the pipe (10 MΩ), the more water can pass through with less resistance. Yet, if there are smaller pipes, some of the water (current) gets used up before it can reach its final destination (output voltage). The optimization of pipe sizes helps ensure more water reaches your tap efficiently.

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