10.1.2. Movement of Electrons

So, here what you see it is that, suppose if we apply the voltage here V and also we apply V keeping body and source they are connected. So, we call this is V and this is DS DS V the current it will be of course, we do have insulator. So, through this terminal there will not be any current, but then there will be a current flow.

In this chunk, we learn about how voltage (V) is applied in an electrical circuit. When a voltage is applied, it creates a current flow; however, some parts of the circuit, such as where an insulator is present, do not allow current to flow. The idea is that while voltages are applied, even an insulator can influence how current behaves in other parts of the circuit.

Think of voltage as water pressure in a pipe. When the pressure (voltage) is applied, water (current) starts to flow. However, if part of the pipe is blocked (like an insulator), water can't flow through that section, but it can still move in the parts that are open.

So, this I it is flowing here. And, of course, this current it is carried by electrons. So, these electrons are really moving from left to right by this field or by this voltage, you may say this is lateral field. So, we can say this vertical field it is getting created by V, which is changing the concentration of the electron on the other hand, the horizontal field getting created by V, which is helping for the movement of the electron from left to right and as a result we do have the I.

This chunk describes how electrons carry current through the circuit. When voltage is applied, electrons move from the source (left) to the drain (right) due to the electric field established by the voltages. The vertical electric field created by one voltage affects electron concentration, while the other voltage establishes a horizontal field that facilitates their movement.

Imagine a racetrack where cars (electrons) move from one side to another. The track's width and length (voltage) affect how quickly the cars can move from the starting point to the finish line. One part of the track makes it easier for cars to start racing, while another adjustment helps them finish the lap.

So, note that these electrons are coming from this side. So, that is why you call this is source and it is getting drained to this terminal that is why you call drain. Now, it is very clear that why you call this is drain and source.

In this section, we clarify what is meant by 'source' and 'drain'. The source is the terminal where electrons originate, while the drain is where they exit the circuit. This terminology helps in understanding the flow of current in devices designed for electronic circuits.

Consider a water fountain where the water (electrons) comes from a tank (source) and flows out through a spout (drain). The tank is where the water starts, and the spout is where it exits, represented by the terms source and drain.

So, this current flow I it is a strong function of this V, V and also it is strong function of the spacing from here to here namely the length of the device. So, it is a strong function of the length it is strong function of the other geometry namely width of the device and also it is strong function of the device parameter, which includes the thickness of this oxide.

This chunk explains the factors that affect the flow of current (I) in a circuit. The current is influenced by the applied voltages (V), the distance between the source and drain (length), the width of the device, and the thickness of materials (like the oxide layer) used in the device. All these parameters need to be considered in the design of electronic devices.

Think of a water slide as an analogy for current flow. The height (voltage), length of the slide (spacing), and the clear path (geometry) all impact how fast a person can slide down. If there’s more friction (oxide thickness), it will slow down the slide, just like it would slow down the flow of electrons.

As a circuit designer what will be looking for if the device it is already fabricated. So, W’s and L’s they are already defined then we will be looking for the dependency of I as function of V and V. And, as a device engineer you may try to change this t you may try to change probably in the surface so that the mobility it will be better and so and so.

In this chunk, we differentiate between the roles of a circuit designer and a device engineer. The circuit designer works with existing devices and focuses on how current (I) changes based on applied voltages, while the device engineer is involved in modifying parameters like oxide thickness (t) to improve electron mobility and device performance.

Imagine a chef (circuit designer) who uses premade ingredients. They focus on how to combine those to make a great dish (circuit). Meanwhile, a farmer (device engineer) works on improving the quality of the ingredients to enhance the flavor of any dish made from them.

On the other hand if it is you are a VLSI circuit designer where the device yet to be implemented. However, technology is fixed; that means, these parameters are fixed. So, you may say that whenever we say technology is fixed device parameters are fixed, but then you also have the flexibility to change the W’s and L’s of the devices.

Here, we discuss the flexibility available to VLSI (Very Large Scale Integration) circuit designers. Even with fixed technology and parameters, they have the freedom to adjust the width (W) and length (L) of the devices, which helps in optimizing their design and performance, especially during the implementation stage.

Consider an architect (VLSI designer) creating a building. They have strict regulations (fixed technology parameters) but can choose how wide (W) and tall (L) the building is to suit their design vision, allowing creativity within the constraints.

--