How does a Mosfet Transistor work? Transistors
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The ENIAC computer took 70 hours to calculate Pi up to 2037 digits in 1949. The smartphone in your hand can now perform the same work in less than half a second. A little device inside the electronic gadget called Transistors enabled this amazing increase in speed.
MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor. Let’s dive into a 3D animation Image to learn how a MOSFET works.
MOSFETs are electronic switches that allow and prevent current flow without the use of mechanical moving parts. A MOSFET is made of a semiconductor material such as silicon, much like any other regular transistor. A semiconductor has an extremely low electrical conductivity in its pure state.
The conductivity of a semiconductor material increases dramatically when a regulated amount of impurities is introduced into it. Doping is the process of introducing contaminants. To comprehend the physics of doping, we must first comprehend Silicon’s internal structure, as well as the structure of the impurity known as a dopant. Because pure silicon has no free electrons, its conductivity is extremely poor.
P-type and N-type
When an impurity with extra electrons is injected into Silicon, however, the conductivity of the resulting material increases considerably. N-type doping is the term for this. Impurities with fewer electrons can also be added to boost the conductivity of pure Silicon. P-type doping is the term for this.
Doping is described as low or light when the impurity concentration is low. If it is higher, though, the doping is referred to as high or heavy. Let’s return to the operation of MOSFETs now. The basic structure of a MOSFET can be created by doping a Silicon wafer in the following manner. It’s worth noting that there are extremely few unbound electrons capable of carrying electricity even in the p region. They’re known as minority carriers. We’ll look at why minority carriers are important in MOSFETs later.
The extra electrons in the end region have a tendency to occupy the holes in the p region whenever a p-n junction is formed. As a result, the p-n junction barrier becomes naturally devoid of holes or free electrons. A depletion region is a name given to this area. The p-n junction of the MOSFET exhibits the same phenomena. Let’s see what happens if we attach a power cell across the MOSFET.
The electrons are drawn to the positive side of the cell and the holes are pushed away at the right-hand p-n junction. In brief, the power source increases the width of the depletion region on the right-hand side. This means that no electrons will travel through the MOSFET. In summary, the MOSFET will not operate with this simplistic setup. Let’s have a look.
How it is possible to have an electron flow in the MOSFET using a simple Technique?
To accomplish so, we must first comprehend the capacitor’s operation. Two parallel metal plates are separated by an insulator inside the capacitor. When you connect these with a DC power supply, the positive terminal of the cell pulls electrons from the metal plate, which then accumulate on the other metal plate. Between the plates, an electric field is created by the accumulation of charge.
Let’s replace one of the capacitor’s plates with the MOSFET’s p-type substrate. The electrons will leave the metal plate if you attach a power source across the MOSFET as indicated, just like in a capacitor. These electrons will be diffused into the p substrate in a MOSFET. An electric field will be formed on the metal plate due to the positive charge induced by the electron displacement, as indicated. Even in the P-type area, there are some unbound electrons. The electrons will be drawn to the top by the electric field created by the capacitive action. We’ll make the assumption that the electric field produced is quite powerful and then watch the electron flow. To be completely clear.
Let’s have a look at the animation again. The holes and some electrons were recombined. After all the holes in the top section are filled, you can observe how it becomes congested with electrons. All the holes were filled just below this location, however, there were no free electrons. This area has now become a new depletion zone. As you can see, this procedure effectively breaches the depletion area barrier, allowing electrons to flow freely.
When we use a power source, as we did at the start of this movie, the electrons flow freely as demonstrated. This is how a MOSFET goes from off to on. The type of the electron flow is simply correlated with the name of the Transistors terminals. If the supplied voltage is insufficient, the electric field will be feeble, and no channel will form, resulting in no electron flow. We will be able to turn the MOSFET on and off simply by adjusting the gate voltage.
Let’s look at a real-world application of a MOSFET as a switch. Take a look at this heat-based fire alarm. The resistance of the thermistor in the circuit reduces as the temperature rises. Because of the high thermistor resistance, the voltage at the gate is initially low at room temperature. And that isn’t enough to turn the MOSFET on. The resistance of the thermistor reduces as the temperature rises.
This results in a high gate voltage, which activates the MOSFET (alarm beeping) and activates the alarm. The MOSFET has paved the way for digital memory and computing. Four MOSFETs have been combined to form the basic memory element of a static Ram in this image. MOSFETs are coupled to construct logic Gates at the most basic level.
The Gates are integrated at the next level to construct processing units that can conduct thousands of logical and arithmetical operations. MOSFETs, unlike BJTs, are scalable devices. In order to produce millions of MOSFETs on a single wafer. When a BJT is turned on, it wastes a small portion of its main current. MOSFETS does not have this kind of power waste. Another benefit of a MOSFET is that it only works with one form of charge carrier, whether it’s a hole or an electron. As a result, it is quieter. MOSFETs are the most preferred choice in digital electronics for these reasons. We hope this article provided you with a clear conceptual understanding of MOSFETs.