65.1.7. Gain Comparison with Common Source Amplifier

So, why did I take this 5 MΩ? It is whatever the parameter we have calculated small signal parameter based on that the equivalent resistance coming here it is 5 MΩ and for that I have taken this is also 5 MΩ, this is also 5 MΩ.

In this chunk, the author discusses the reason behind using 5 MΩ as the load resistance in the circuit. This choice is based on small-signal parameters calculated for the circuit. The author emphasizes that by opting for an active load, they aim to achieve a higher gain in the amplifier design.

Imagine trying to lift a very heavy object. If you use a lever that’s designed effectively (like the active load), you can significantly increase the lifting power you have (higher gain). If you use just your hands with no tools (passive load), it may be very difficult, requiring more effort for less result.

So, and if we see the value of this R it is 5 M and g it is 2 mA/V. So, that gives us this is 10‒3 and here we do have 5 × 106 that gives us ‒ 5000.

In this section, the calculation of voltage gain is being discussed. The author explains how to obtain the voltage gain by using the resistance value and small signal parameters. Here, the result shows a significant increase in gain from a basic circuit configuration—indicating the effectiveness of the cascode amplifier with an active load.

Think of it as converting a tiny whisper (the weak initial voltage) into a loud voice (the amplified output). The circuit designed like a megaphone (cascoding design with the right parameters) can make that whisper sound like a shout, dramatically increasing the power of the sound.

So, to get the input capacitance C which is C + C (1 ‒ whatever the gain we do have from here).

This chunk focuses on the calculation of input capacitance in the circuit after the gain has been applied. The author outlines that the input capacitance can change due to the gain, showing how it can potentially increase or affect circuit performance. This aspect is crucial in understanding the trade-offs involved when designing amplifiers.

Consider trying to fill a balloon (the capacitor) with air. If you try to inflate a small balloon with a lot of air (high gain), it will take more effort and might pop (increase in capacitance). The trade-off is balancing how much air (gain) you put in without exceeding the balloon’s limits.

In summary if I compared this cascode amplifier to boost to the gain and if I compare the performance of the standard common source amplifier.

Here, the author summarizes the key differences between the cascode amplifier and the standard common source amplifier. The discussion highlights that while the cascode design can achieve much higher gain, it may also impact bandwidth and other performance parameters. This comparison helps illustrate why and when to select different amplifier configurations based on needs.

Imagine two cars: one (cascode amplifier) is designed for speed (high gain), while the other (common source amplifier) is built for agility (high bandwidth). Depending on whether you need to race to your destination or navigate through tight spaces, you would choose one over the other. Each has its strengths!

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