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MOSFET – the most common transistors used today

MOSFET–overview of the most common transistors used today

Semiconductor surface is an important factor affecting the performance of semiconductor devices, and the development of semiconductor devices has promoted the development of some surface devices such as MOSFET and CCD.

Among them, MOSFET is a field effect transistor that can be widely used in analog and digital circuits. The core of MOSFET is metal, oxide layer and semiconductor capacitor. We will have a comprehensive understanding of MOSFET through this article.

What is MOSFET in PCB?

MOSFET, its full name is metal oxide semiconductor field effect transistor. This is a semiconductor device that is utilized as a switch in the electric circuit for high voltage control as well as for amplification of electric signals resulting in better performance of electric circuits. It is encapsulated in a very small size chip which is used in digital and analog circuits. As they are power devices, so they are used to control the loads as per the requirement.

It is said that without MOSFETs the latest technological development would not have been possible. The reason is they require less current for load current control. Let’s dive deep into the details of MOSFETs.

What are types of MOSFET?

Generally MOSFET can be divided into two categories:

● Enhancement mode MOSFET

In this classification, the level of conductivity increases by increasing voltage on the gate terminal. When there is no voltage on the gate terminal the device does not conduct and hence it acts as an open switch. The carriers increase the conductivity of the channel due to electrons or holes depending on the N-type or P-type channel respectively which is done by increasing the oxide layer.

● Depletion mode MOSFET

The zero voltage on the gate terminal increases the level of conductivity as no resistance afterward so it acts as a closed switch but if the voltage is negative or positive then the conductivity would drop to zero.

The conductivity of MOSFETs in this mode is less as compared to enhancement MOSFETs because the gate terminal is covered by a thin layer of silicon.

These two modes help in making it act like a switch.

What is the advantage of MOSFET?

People often compare MOSFET with traditional junction FET, or JFET, but MOSFET has more advantages. No matter what the gate voltage is, no flow of electrons so eventually current between the gate and the channel since the gate is electrically isolated from the channel.

The MOSFET effectively has an infinite impedance as a result. MOSFETs are hence advantageous for power amplifiers. Applications requiring high-speed switching can also benefit from the devices. Computers use integrated circuits (ICs) that have little MOSFETs in them.

What is the disadvantage of MOSFET?

Electrostatic charges have the potential to permanently destroy the MOSFET since the oxide layer is so thin. Any amount of electrostatic accumulation can permanently damage a MOSFET. MOSFET devices typically don’t perform as well in RF work with weak signals as other FET kinds do.

The voltage across a power MOSFET is high in the on state. In comparison to a power transistor, the on-state power dissipation is therefore very considerable. Power MOSFETS are capable of asymmetric filtering. High forward voltages can be blocked, while reverse bias voltages cannot. Therefore, a diode must be connected across the power MOSFET to protect it from damage as they already have short life.

What is a MOSFET used for?

MOSFET is a voltage control element. FET is often used in the input stage of multistage amplifier for impedance transformation. In addition, it can also be used as an electronic switch, a variable resistor, and a convenient constant current source. They can also be utilized as signal amplifiers and to change the conductivity levels for analog circuits.

Power MOSFETs are often used to regulate with high currents and high power circuits. These are separate components that are packed as a single transistor with a high capacitor. MOSFET is frequently applied in analog and digital circuits, motor controllers and switching power supplies.

These basic uses in normal day life give it more priority over BJTs. So, they are used in high radio frequency, light sensing devices, electric vehicles for stopping battery usage, and signal transmission.

What is the structure of MOSFET?

Three terminals—a source, gate, and drain—make up the device. These are all present in a material called substrate that is connected to the source for practical applications.

A voltage-controlled FET with a metal oxide gate electrode is known as a MOSFET. The MOS structure’s metal has a gate attached to it. A thin insulating silicon dioxide dielectric layer separates the gate electrode from the primary semiconductor, which may be an n-channel or p-channel. There are two n-type regions immediately below the source and drain terminals.

What are characteristics of MOSFET?

The depletion and enhancement modes have an impact on the MOSFET’s properties as well.

● Characteristics of Enhancement Mode
The MOSFET’s most popular transistor is an enhancement kind. This kind doesn’t demonstrate any conduction if the voltage at the gate and source terminals is zero. As the voltage approaches the threshold, the conductivity tends to increase.

● Characteristics of Depletion Mode
The applied voltage at the terminal gate determines the width of the depletion region in this mode. The width of the depletion region will rise if it is raised in terms of the positive polarity to be considered. Rarely is this type of transistor preferred in PCB design.

What is the difference between MOSFET and transistor?

The current is controlled by a BJT transistor. This means that the current entering the transistor’s base regulates the current entering its collector.

A voltage-controlled device is a MOSFET. The amount of current that goes into the drain is determined by the voltage you apply across the gate.
In other words, they act in a different way. Although they are both transistors, they serve different purposes.

An example of a transistor with a high input impedance is a MOSFET, which contains a metal oxide film on the gate (equivalent to the base of a bipolar transistor). Therefore, a MOSFET has the source, while the bipolar transistor has the collector and a MOSFET has a gate, whereas a bipolar transistor has a base. The drain in a MOSFET serves as the emitter in a bipolar transistor.



Is MOSFET active or passive?

They are active. They behave differently to voltage and current as they tend to amplify an electric signal.

How do you read a MOSFET?

This requires a bit of detail but let me describe it briefly for your better comprehension. We have NMOS and PMOS. In these, we have a gate on left, a source on the bottom, and a drain on top. The base is in middle on the left side of MOSFET. Physically, you can detect these terminals of MOSFETs from a digital multimeter that either it’s a drain, gate, or source.


MOSFETs are active tri-terminal efficient electronic components use for mainly switching and amplification purposes. Depending on their substrate they could be NMOS and PMOS. The MOSFET effectively has an infinite impedance. The voltage across a power MOSFET is high in the on state.

I hope the information provided in this article made you understand MOSFETs in a better way and for information you can check IBE website where you can find more articles about electronic components as well as many other informational articles!Meantime, please contact us if you are looking for a one-stop PCBA manufacturer who can provide PCB design, SMT/DIP assembly, package service and so on.



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