64.4.1. AC Analysis Overview

Now it may be a situation where this resistance it may be small or whatever the cutoff frequency we are obtaining by this R and then C and R that may be beyond the upper cutoff frequency defined by R and the C. So, far such case you may say that then what is the advantage of cascode amplifier. 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 notable advantages compared to standard amplifiers. First, it can extend the bandwidth of the circuit, particularly when the source resistance is large. This allows the amplifier to handle a broader range of frequencies without significant loss of signal. Second, cascode amplifiers are known for their ability to drastically increase the gain, which is the amplifier's ability to magnify the input signal. These two advantages are essential, especially in high-frequency applications, where bandwidth and gain are critical factors.

Imagine a road (the bandwidth) where cars (signals) travel. If the road is too narrow (low bandwidth), only a few cars can fit at a time, causing traffic jams (signal distortion). A cascode amplifier acts like expanding that road width, allowing more cars to pass through efficiently. Additionally, think of gain as the ability to amplify the voice of a speaker in a large area. The cascode amplifier functions like a powerful microphone, making the speaker's voice heard even in the furthest corners of the hall.

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.

In this section, we consider how to effectively increase the gain of a cascode amplifier by replacing passive components with active circuits. An active circuit can provide better support for the signal, thus allowing the gain to be amplified significantly. The focus on varying the resistance in the circuit (from 2.8 kΩ to 10 MΩ) illustrates how these changes impact the overall performance and efficiency of the amplifier.

Think about using a regular hearing aid versus a powerful sound system. A hearing aid can help a person hear better, but might struggle in a noisy environment. Now imagine enhancing that hearing aid into a robust sound system that can manage a crowded concert—this system would amplify sound much more effectively. Similarly, increasing the gain in a cascode amplifier improves its signal amplification capability.

So, naturally the output voltage it will be 12 V. On the other hand if I consider practical circuit and let me use the analysis slight analysis here...

After modifying the circuit to assess how changes influence voltage levels, we realize it leads to a higher output voltage of 12 V under certain conditions. This sets the stage for understanding how voltage is impacted by different configurations within the amplifier circuit, particularly when analyzing how the transistors operate in their active regions and how their respective resistances interact.

This scenario is akin to adjusting the water flow through pipes. If you increase the water pressure (voltage), the amount of water (current) coming out can substantially increase. In a similar manner, changes to the amplifier circuit can significantly boost the output voltage, enhancing the output signal.

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