81.2.1. Overview of Circuit Analysis

So, this application and this application circuit all together they are different. But as long as we ensure that M2, M3, and M1 are similar in nature, then we can say that this current I3 it is also satisfying all these conditions and so, this I3 it can be obtained from the same reference current.

In circuit analysis, different applications may involve various circuit designs, but they can operate under similar principles. The key is to ensure that components (referred to as M2, M3, and M1) have similar characteristics. When these components behave similarly, it allows the current (I3) to be derived from a common reference current, establishing consistent performance across the circuits.

Think of making a smoothie. You can use different fruits (similar to variations in circuits) like bananas, strawberries, or mangoes, but if they all blend smoothly together, the final product (analogous to current I3) will have a consistent taste (performance) if you prepare it in the same way.

In fact, you can generate n number of such kind of current references. So, if you have one good current reference from that you can have many more current references you can generate right.

The concept here is about scalability in circuit design. If you establish a single reliable reference current, you can create multiple additional currents based on that reference. This is significant in electronic design as it allows for the development of complex circuits that maintain performance based on a single standard.

Consider a main water supply in a neighborhood. If there is a strong and reliable water source (the reference current), several houses (additional currents) can tap into that source for their individual water needs. This ensures all houses have adequate water flow and pressure, illustrating how one reference can support multiple outputs.

So, that is why; that is why we are using current mirror.

A current mirror is a device or configuration in circuit design that copies current from one active device to another. This is an essential concept for maintaining consistent currents in different branches of a circuit, thereby improving performance and efficiency.

Think of a copy machine in an office. When you want multiple copies of the same document, the machine takes one original and produces many identical copies. Similarly, a current mirror takes one current and replicates it across multiple circuits, ensuring uniformity.

So, this is MOSFET version current mirror. And we can have a BJT counterpart.

There are different types of components used for current mirrors, primarily MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and BJTs (Bipolar Junction Transistors). Each has its own characteristics and advantages, but both can serve the purpose of creating a current mirror, allowing designs to be adapted based on specific circuit needs.

Imagine using different tools for carpentry. A hammer (BJT) and a screwdriver (MOSFET) can help you accomplish similar tasks (like making a stable structure) but in different ways. Depending on the job at hand, you would choose the tool that best fits the task, just as engineers choose between MOSFETs and BJTs for their specific applications.

So, in the next slide we are having the current reference here. So, you can see here it is very similar; this circuit is very similar only thing is that we do have Q1 and Q2 instead of M1 and M2.

This chunk discusses the configuration of a current reference using BJTs instead of MOSFETs. The layout and function remain consistent, but the components used (Q1 and Q2) are transistor variants that have distinct characteristics. This transition highlights the adaptability of current reference designs in circuit analysis.

Think of replacing ingredients in a recipe with alternatives. If you are making a cake, you could use flour, but if you prefer a gluten-free option, almond flour can be a replacement. Both serve the same purpose of making the cake, just in slightly different ways, much like how BJTs can replace MOSFETs in similar circuit designs.

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