65.1. Analog Electronic Circuits

Welcome back after the short break. So, we are talking about the Cascode Amplifier using BJT sorry MOSFET. BJT part we already have completed now come here so, far we are talking about the passive load namely R it was 2 k now we are going to change this load to active kind of load, where our basic motivation is to for higher gain.

In this chunk, we are introduced to the topic of the Cascode Amplifier, where the speaker highlights that they will focus on using MOSFETs instead of BJTs. The previous discussions around BJTs have concluded, and now the emphasis is on transitioning from a passive load (2 kΩ resistor) to an active load to achieve a higher gain. The purpose of an active load is to enhance performance, particularly the gain of the amplifier.

Imagine you are trying to lift a heavy box. If you use a lever (active load), it makes it much easier to lift the box compared to just pushing it without any help (passive load). In electronics, switching from a passive to an active load acts as a lever, making it easier to achieve higher gain in a circuit.

So, we do have; so, we do have the cascode amplifier here with active load namely the I here it is 2 mA current and this R it is 5 MΩ please read as this R as 5 MΩ.

In this chunk, the speaker specifies parameters of the cascode amplifier configuration. The current (I) is set at 2 mA, and the load resistance (R) has been corrected to 5 MΩ. These parameters are crucial as they directly impact the performance of the amplifier, including its voltage gain and output characteristics. Understanding these values helps in calculating how well the amplifier will perform under specific conditions.

Think of these parameters like the ingredients in a recipe. If you want to bake a cake (build a circuit), you need the right amounts of flour (load resistance) and eggs (current). Using too little or too much of any ingredient will change how your cake turns out, just as varying parameters in a circuit changes its performance.

So, with this we need to find what will be the voltage gain. Now for that we need to know what will be the equivalent resistance coming here and this equivalent resistance it = ( ).

This chunk focuses on calculating the voltage gain of the cascode amplifier. To determine the voltage gain, it’s important to first ascertain the equivalent resistance connected to the circuit. The speaker hints at a formula, although it seems incomplete in this extract. Understanding voltage gain is vital, as it is a measure of how much the amplifier boosts the input signal, directly affecting the effectiveness of the amplifier.

Consider the voltage gain as the volume of music coming from a speaker. If the speaker is very powerful (high gain), it can amplify the sound louder even from a quiet source. Just like in a circuit, if the amplifier has a high voltage gain, it can produce a significantly louder output from a small input.

So, to get the maximum advantage what about the resistance we got from this circuit lower part, if we take the same resistance then we can get the maximum benefit for both the gain as well as bandwidth consideration.

In this section, the speaker explains the importance of having the right resistance from the lower part of the circuit. Using the same resistance helps maximize both gain and bandwidth. Bandwidth is critical in electronics as it describes the range of frequencies the amplifier can handle effectively. Thus, the choice of resistance not only affects gain but also how well the amplifier performs across different frequencies.

Think of bandwidth like the size of a highway. If the highway is wide (optimal resistance), it can handle more cars (signals) efficiently. If the highway is narrow (wrong resistance), traffic will become congested, limiting how many cars can pass at once, similar to how a circuit’s performance deteriorates with inappropriate resistance settings.

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.

Finally, this chunk sums up the comparison between the cascode amplifier and the standard common source amplifier. While the common source amplifier might have lower gain, it delivers high bandwidth due to its design. Conversely, the cascode amplifier significantly boosts the gain but may compromise bandwidth. It’s important to understand trade-offs in amplifier design, where engineers must choose between gain and bandwidth based on application needs.

Imagine a sports car (cascode amplifier) that can go really fast (high gain), but cannot carry many people (low bandwidth). In contrast, a minivan (common source amplifier) may not go as fast, but can carry a lot of passengers (high bandwidth). Depending on your need, you might choose one over the other.

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