The Engineering Projects

MOSFET WHAT A MOSFET IS AND HOW IT WORKS

Hi Guys! Hope this finds you well. Thank you for clicking this read. In this post today, I'll walk you through the Mosfet what the Mosfet is and how it works. The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistor is a semiconductor device widely used for switching and amplifying electronic signals. The MOSFET is a core of integrated circuit and it can be designed and fabricated in a single chip as they come in small sizes. The MOSFET carries four-terminal called: source(S), gate (G), drain (D) and body (B) terminals. The body of the MOSFET is connected to the source terminal, making it a three-terminal device like a field-effect transistor. The MOSFET is a common transistor that is used in both analog and digital circuits. The MOSFET works by electronically varying the width of a channel that contains charge carriers i.e. electrons or holes.  The charge carriers enter the channel at the source terminal and exit via the drain terminal. The width of the channel is controlled by the voltage on a gate terminal that is located between source and drain. It is insulated with an extremely thin layer of metal oxide.

The MOSFET can function in two ways

• Depletion Mode
• Enhancement Mode

Depletion Mode:

When there is no voltage on the gate, the channel shows its maximum conductance. As the voltage on the gate is either positive or negative, the channel conductivity decreases.

Enhancement mode:

When there is no voltage on the gate the device does not conduct. More the voltage on the gate, the better the device can conduct.
Video courtesy of Teko Broadcast.

Working Principle of MOSFET

• The MOSFET controls the voltage and current flow between the source and drain. It works almost as a switch. The working of MOSFET depends on the MOS capacitor. The MOS capacitor is a critical part of the MOSFET.
• The semiconductor surface at the below oxide layer is located between source and drain terminals. It can be inverted from p-type to n-type by applying positive or negative gate voltages respectively.

• When we apply the positive gate voltage the holes present under the oxide layer are pushed downward with the substrate. The depletion region is populated by the bound negative charges which are associated with the acceptor atoms, thus forming the electron reach channel.

• The positive voltage also attracts electrons from the n+ source and drain regions into the channel.
• Now, if a voltage is applied between the drain and source, the current flows freely between the source and drain and the gate voltage controls the electrons in the channel.
• Instead of a positive voltage, if we apply a negative voltage, a hole channel will be formed under the oxide layer.

• P-Channel MOSFET:

• The P-channel MOSFET has a P-channel region between source and drain. It is a four-terminal device such as a gate, drain, source, body.
• The drain and source are heavily doped p+ region and the body or substrate is n-type. The flow of current is due to positively charged holes.

• When we apply the negative gate voltage, the electrons present under the oxide layer are pushed downward into the substrate with a repulsive force.
• The depletion region is populated by the bound positive charges which are associated with the donor atoms. The negative gate voltage also attracts holes from p+ source and drain regions into the channel region.

• N- Channel MOSFET:

• The N-Channel MOSFET has an N-channel region between the source and drain. It is a four-terminal device such as a gate, drain, source, body.
• In this type of MOSFET, the drain and source terminals are heavily doped n+ region and the substrate or body is P-type. The current flows due to the negatively charged electrons. When we apply the positive gate voltage, the holes present under the oxide layer pushed downward into the substrate with a repulsive force.
• The depletion region is populated by the bound negative charges which are associated with the acceptor atoms, thereby forming the electron reach channel.

• The positive voltage also attracts electrons from the n+ source and drain regions into the channel.
• Now, if a voltage is applied between the drain and source, the current flows freely between the source and drain and the gate voltage controls the electrons in the channel.
• And if we apply a negative voltage, a hole channel will be formed under the oxide layer.

MOSFET SWITCH

• In this circuit arrangement, an enhanced mode and N-channel MOSFET is being used to switch a sample lamp ON and OFF. The positive gate voltage is applied to the base of the transistor and the lamp is ON (VGS =+v) or at zero voltage level the device turns off (VGS=0).

• In the above circuit, it is a very simple circuit for switching a resistive load such as a lamp or LED. But when using MOSFET to switch either inductive or capacitive load, protection is required to contain the MOSFET device.
• For the MOSFET to operate as an analog switching device, it needs to be switched between its cutoff region where VGS =0 and saturation region where VGS =+v.
• MOSFET is also a transistor. We abbreviate it as Metal Oxide Silicon Field Effect Transistor. It will have P-channel and N-channel. It consists of a source, gate, and drain. Here we connected a resistive load of 24O in series with an ammeter, and a voltage meter connected across the MOSFET.

• In the transistor, the current flow in the gate is in a positive direction and the source goes to ground. In BJT’s, the current flow is the base-to-emitter circuit. But in MOSFET there is no current flow because there is a capacitor at the beginning of the gate, it just requires a voltage.
• We will get to know this by doing the simulation process by switching ON/OFF. When the switch is ON there is no current flow in the circuit, when we have taken a resistance of 24O and 0.29 of ammeter voltage then we find the negligible voltage drop across the source because there is +0.21V across MOSFET.
• The resistance between drain and source is called RDS. Because of RDS, the voltage drop appears while current flow in the circuit. RDS varies depending on the type of MOSFET (it could be 0.001, 0.005, and 0.05 depending on the voltage type).
• Finally, we will conclude that the transistor requires current whereas MOSFET requires a voltage. The driving requirement for the MOSFET is much better and simpler as compared to a BJT.

What is a Semiconductor? Types, Examples & Applications

Hello Friends, I hope you’re well today. Today, we are going to start a new tutorial series on Semiconductors. In this series, we will discuss the semiconductor components, devices, etc. in detail. We will start from the very basics and will gradually move towards complex concepts.

As today's our first tutorial in this series, we will discuss the basics of semiconductors. So, let's get started:

What is a Semiconductor?

• A Semiconductor Material is defined by its ability to conduct electricity and its conductive properties lie between conductor and insulator, normally ranging between 10^-6 to 10^-4 (Ωm)^-1.
• Under specific conditions, Semiconductors have the ability to act either as a pure conductor or a pure insulator.
• Examples of Semiconductor materials are Silicon, Germanium, Gallium Arsenide etc., where Silicon is the most commonly used.
• Gallium arsenide stands as the second-best semiconductor material and is used in solar cells, laser diodes, microwave frequency integrated circuits etc.

Why Semiconductors?

The main advantage of a semiconductor is its ability to control the flow of electrical current(electrical charges) by creating a PN Junction. The conductors lack this ability as they allow current to flow in both directions. We will discuss PN Junction in our next lecture.

In order to understand the conductive behavior of semiconductors, we need to understand their construction and Energy Levels:

Electrical Properties of Solids

After the discovery of electricity(credit goes to Benjamin Franklin), scientists have divided earthly materials into 3 main categories, depending on their electrical conductivity, titled:

1. Conductor: has the ability to conduct electricity i.e. Copper, Silver, Gold, Aluminium etc.
2. Insulator: doesn't allow electrical charges to flow through it i.e. Plastic, Diamond, Rubber etc.
3. Semiconductor: A material whose properties stand between conductor and insulator i.e. silicon, germanium, gallium arsenide etc.

This diversity in the conductive behavior of solids failed Bohr's model of free electrons. Instead, the Energy Band Theory based on Wave Mechanical Model was used to explain it.

So, in order to understand the conductive behavior of solids, we need to first have a look at the Energy Band Theory:

Energy Band Theory

As we know, a solid atom has various energy bands filled with electrons. In all these energy bands, the electrons remain bound to the nucleus and have distinct energy levels. The electrons present in the outermost energy band of an atom are called valence electrons and the outermost band itself is called valence band.

Above the valance band, we have another band called Conduction Band. The Conduction Band also has electrons but these electrons are not bound to the Nucleus of the atom and are thus called Free Electrons or Conductive Electrons. The electricity passes through solids because of these free electrons present in the Conduction Band.

There's an empty space present between the Valance Band and Conduction Band, which has no electrons and is called Forbidden Energy Gap. The arrangement of the Valence Band, Conduction Band, and Forbidden Gap is shown in the below figure:

Now let's have a look at the effect of this Energy Band Theory on Solids' Electrical Behavior:

Conductive Behavior of Solids

The valance electrons in the outermost shell(valance band) keep on trying to escape to the conduction band but because of their low energy levels and the forbidden gap in between, they couldn't escape. So, in order to move the electrons from the Valence Band to the Conduction band, we need to provide external energy to these electrons.

As you can see in the above figure, there's no Forbidden Gap in the Conductors and the Valence & Conduction Bands are overlapping. That's why, when we provide external energy i.e. electricity, the current easily passes through it. The conductivity behavior of conductors is normally 10⁷ (Ωm)^-1.

In the case of Inductors, the forbidden energy gap is quite big(several eV) and thus the conduction band has no free electrons. Even if we provide external energy to it, the electrons from the Valance Band won't be able to cross the forbidden gap. The Inductors have conductivity ranging between 10^-10 to 10^-20 (Ωm)^-1.

In Semiconductors, we have a very small forbidden energy gap(around 1eV) and that's why we have few free electrons present in the Conduction Band. At 0K temperature, the Conduction Band of the Semiconductor has no electrons, as all electrons are present in its valance shell. But on increasing the temperature, the electrons get sufficient energy to jump from the valance to the conduction band. So, at 0K, the semiconductor will behave as an insulator but at room temperature, it will behave as a semiconductor. The conductivity of semiconductors lies between 10^-6 to 10^-4 (Ωm)^-1.

I hope, now you have a complete understanding of Semiconductors' electrical behavior.

What are semiconductors used for?

Semiconductors have brought a revolution in the field of electronics. Semiconductors are used for designing electronic/embedded components. Let's have a look at a few of its applications:

• The most commonly used semiconductor component is the Diode., which allows the flow of current in one direction only and thus acts as a one-way electronic valve.
• After the diode, transistor was invented, which is used for fast switching and current amplification.
• The invention of the diode & transistor opened the door to nanotechnology and new integrated chips were designed i.e. MAX232, ULN2003, CD4050 etc.
• All the integrated chips used in Embedded Systems(i.e. Microcontrollers, Microprocessors etc.) have semiconductor components embedded in them.
• Semiconductor has brought automatic control in electronic circuits, which isn't possible with conductors.

Types of Semiconductors

Engineers have divided Semiconductors into two main types, named:

1. Intrinsic Semiconductors.
2. Extrinsic Semiconductors.

Let's discuss both of them, one by one:

Intrinsic Semiconductors

• Semiconductors in their pure form are called Intrinsic Semiconductors and are barely useful as they are neither good conductors nor good insulators.
• In the pure form, the valence shell(of semiconductor material) carries an equal number of holes & electrons(silicon has 4 valence electrons).

Extrinsic Semiconductors

• Impurities(i.e. Boron, Arsenic, Antimony etc.) are added to the pure Semiconductors by a method called Doping, which increases the conductive behavior of semiconductors and such doped semiconductors are known as Extrinsic Semiconductors. (We will discuss doping shortly)

Depending on the doping material used, extrinsic semiconductors are further divided into two types, named:

• N-Type Semiconductors.
• P-Type Semiconductors.

N-Type Semiconductors

• When a Pentavalent Material(having 5 valence electrons) is used as a doping agent, four of its electrons in the valence shell create covalent bonds with the neighboring Si atoms, while the 5th electron(of the Pentavalent element) becomes a Free Electron. Such extrinsic semiconductors are called N-Type Semiconductors.

• In N-Type Semiconductors, the majority charge carriers are electrons(negatively charged).
• Pentavalent Elements normally used in the doping process are Antimony, Arsenic, Phosphorous etc.
• As a semiconductor is accepting a free electron, it is termed an Acceptor, while the pentavalent element is termed a Donor, as it's donating its electron.

P-Type Semiconductors

• When a semiconductor material is doped with a Trivalent Material(having 3 valence electrons), the 3 electrons of the trivalent element create covalent bonds with the Si atoms nearby but it couldn't provide the 4th electron and thus creates a hole(positively charged), which is actually a vacancy & waits for an electron to join. Such doped semiconductors are called P-Type Semiconductors.

• In P-Type Semiconductors, the majority charge carriers are holes(positively charged).
• Examples of Trivalent Elements used in the doping process are Boron, Gallium, Aluminium, Indium etc.
• The trivalent element is Acceptor here, while the semiconductor is Donor.

Doping of Semiconductors

• As we have discussed earlier, a semiconductor in its pure form acts as an insulator as it has an equal number of electrons and holes in its outermost shell(called the valence shell) .
• So, in order to generate conductive properties in semiconductors, a strictly controlled quantity of impurity(i.e. arsenic, boron etc.) is added by a method called Doping. (We will discuss Doping in detail in our next lecture on PN Junction)
  
• The intensity of conductive behavior depends on the type & quantity of impurity added.
• Two types of impurity elements are normally used, which are:
  • Pentavalent: Creates N-Type Semiconductors.
  • Trivalent: Creates P-Type Semiconductors.

PN Junction in Semiconductors

• If a single semiconductor material is doped with both trivalent & pentavalent impurities, both P-Type & N-Type regions are created in a single substance.
• As a result, a special barrier is created at the boundary of these two regions, which stops the flow of charge carriers and is called the PN Junction.
• This PN Junction formulated the basis of the first semiconductor component called the Diode. (We will discuss in the next lecture)
  
• Different variations of PN junction resulted in the creation of other basic components i.e. transistor, FET, MOSFET etc.(We will cover all of these in our upcoming lectures)

Now, let's have a look at a few examples of Semiconductor materials:

Semiconductor Materials

There are numerous Semiconductor materials available, a few of them are as follows:

1. Group IV of Periodic Table

• In modern IUPAC notation, it's termed as Group 14 of the Periodic Table while in semiconductor circle, it's still considered as Group IV.
• Group IV elements are the most commonly used semiconductors but few elements of this group have large band gaps and thus act as insulators.
• Semiconductors present in this group are Carbon, Silicon, Germanium, tin.

2. Compound Semiconductors

• Compound Semiconductors are designed by the chemical combination of two different elements.
• Compound semiconductors are normally designed by using elements from Group III & V of the periodic table.
• A few examples of compound semiconductors are Gallium Arsenide, Silicon Carbide etc.

3. Organic Semiconductors

• Organic semiconductors contain polymer structures, normally composed of carbon or hydrogen.
• The first organic semiconductor discovered was Bechgaard salt (TMTSF)₂ PF₆ in 1980.

4. Liquid/Amorphous Semiconductors

• Normally semiconductors are available in solid-state but few liquid/amorphous semiconductors are also discovered i.e. hydrogenated amorphous silicon.
• Few oxides and alloys also depict semiconductor behavior.

Applications of Semiconductor Materials

In today's world, electronics (especially embedded) will simply die if we remove semiconductor components from it. The semiconductor has applications in almost every sector of electronics. Let's have a look at a few applications of Semiconductors :

1. Consumer Goods(Electronics)

• We can't think of a world without Electronic devices(i.e. mobile phones, laptops, microwaves, refrigerators etc.).
• All these appliances are using semiconductor components(i.e. diode, transistor, MOSFET, integrated chip etc.) in their electronic control units.

2. Embedded Systems

• Microcontrollers/Microprocessors have revolutionized the world and are considered the base of Embedded Systems.
• These embedded controllers have nano transistors(semiconductor components) embedded in them, acting as smart switches.
• So, semiconductors play an important role in embedded systems as well.

3. Thermal Conductivity

• A few semiconductors have high thermal conductivity and are thus used as a cooling agent in thermoelectric applications.

4. Light Emitting Diode

• Instead of heat, a few semiconductors also produce light and are thus used in LEDs, OLEDs etc.
• These semiconductors are normally available in liquid or amorphous form and are used as a thin-coated film.

That’s all for today. I hope you find this article helpful. Today, we discussed the basics of Semiconductors i.e. what are semiconductors, why semiconductors? Semiconductor examples, semiconductors applications, properties of semiconductors, semiconductor companies, most commonly used semiconductor materials etc. in detail. If you have any questions you can approach me in the section below. I’d love to help you the best way I can. You are most welcome to pop your suggestions in the comment section below, they help us create quality content. Thanks for reading this post. :)

A 21st Century Tire Industry Will Revolutionize The Market

Hi Friends! Hope you’re well today. I welcome you on board. In this post today, I’ll explain how a 21st century tire industry will revolutionize the market. Tire changing and purchasing is a controversial issue for many Americans, with non-insurance purchases that are often arguably expensive. This is set to change with the rise of Tire Agent, who TechCrunch highlighted as receiving $5m in new financing in their bid to remove the mystique from tire purchasing and installation. Using smart data, they’re aiming to pull together buyers, sellers, and mechanics across the country and provide a truly equitable purchase map for those in need. With this data, the industry will be revolutionized, and technology will change how motorists deal with their tires forever in much the same way solar energy has transformed the market already.

Hidden information

One of the aims of the startup is to provide engineering information directly to customers. This would be a huge overhaul for American drivers; the NY Post estimates that 68% of motorists are not only lacking knowledge about their vehicle, but they're scared of repairing it too. With the data on offer from these startups, motorists will have the confidence to do tire changes, know how to efficiently check tire pressure, and potentially tackle more challenging costs – or at least run diagnostics before they get to the shutters of the mechanics' shop. Straight away, this will lead to changes in how tire engineering is viewed, with a movement towards the consumer market required, and less focus is given to the needs of mechanic shops and the closed-shop market.

Better pricing, better innovation

Arguably, the cost of tires and the labor that goes into replacing older models stymies innovation. If the tires work, and the market is enjoying the profit margin, there is less impetus for engineers to invent new forms of the tire and get them into that consumer market. With the impetus shifted away from costly mechanic shops and into the consumer’s wallet, it’s likely that more innovation will be seen – after all, with the wealth of information available to them, consumers will make the smartest and most long-term pick available to them as opposed to simply working from time-tested recommendations from the shop or the manufacturer. This is already creating the need for innovation in tires.

Changing with the weather

A primary reason for road users to get into the garage is to have weather-hit tires repaired or adapted. Think snowshoe and chain in winter, or rubber reinforcements on particularly hot asphalt. Increasingly, tires are starting to actively adapt to the weather, reducing the necessity for any changes at all off the road. According to CNET, Continental has been market leaders with this innovation though many businesses have created their own variants. What does this mean for consumers? Once again, putting the entire functionality and adaptability of the vehicle back into their hands will mean less time with the mechanic and a greater degree of control over what their car is going to do and how it performs. It might even help consumers to get more involved with the technology behind tire engineering.

A self-sealing future?

Self-sealing tires are common these days, but they have their drawbacks. In August 2019, CNBC raised the prospect of fully self-repairing, smart tires. Similarly, Michelin debuted a tire that doesn’t need to be inflated at all. With these smart tires on the market, the engineering outlook for tires and vehicles, in general, will be completely changed – the focus will be shifted onto improving these innovations and making them suitable for a wider market, and easily accessible for vehicles of all types. This once again gives more power to the consumer, pulling them away from mechanics and towards being positive about the technology they can deploy their vehicles to keep them on the road and healthy for longer

Ultimate energy efficiency

Pairing with the sustainable goals of the seal-sealing tire is the car-charging tire. As tires produce motion and potential energy that has the potential to be turned into actual efficient energy for the car to deploy. According to Interesting Engineering, this is becoming a reality that will help to see cars self-powered to an even greater degree. Goodyear’s BH03 concept is nothing new that was released in 2015 and has seen huge developments since then. Now, the concept is being plugged for active use, first in electric vehicles to give primary drive power but also, potentially, in combustion vehicles, to provide plenty of ways of charging the car battery that relies on sustainable tools.

Holistic benefits

Whatever form cars take, it’s undeniable that they add emissions to the world – this is true whether from a classic combustion engine emissions, or the carbon cycle of producing any other vehicle. Can tires combat this? Another Goodyear concept focuses on their ‘Oxygene’ concept, which adds biological material to the outside of the tires. The purpose of this is to actively filter onrushing air from the car as it travels, producing net benefits for the air around the vehicle as it moves. This seems like wishful thinking but these ‘green benefits’ are being used across a wide range of industries – for instance, green roofing has been a norm in many American cities for years now. It might not be too long until the average road user sees hundreds of green hubcaps and tires as they take their drive across the nation’s roads – and that they’ll enjoy the benefits, too, with clean air on the way. With this new generation of tires being green energy focused, this could easily mean a wholesale shift in tire production. A relatively static market can start to fully utilize materials science to innovate new products. This will be demonstrated in a huge range of products, but with sustainability often the goal, expect innovation hours and cash to be plunged into the likes of self-sealing tires and sustainable EV products. This will ultimately benefit the wider market and thus the engineers looking to make their name in the auto industry.