Metal-Oxide Semiconductor Field Effect Transistor, referred to as MOSFET. It is a fundamental building block of modern electronics and the most commonly used device in history. The shrinking and miniaturization of MOSFETs has been driving the rapid development of electronic semiconductor technology and enabling high-density ICs such as memory chips and microprocessors
MOSFET has the advantages of high input impedance, low noise, good thermal stability, and strong radiation resistance. At the same time, it also has the characteristics of small size, light weight, low power consumption, and long life.
Different Type of MOSFET
MOSFETs are common in digital and power applications due to their advantages over bipolar transistors:
MOSFET devices are very important in high-frequency switching applications. MOSFET transistors are easier to drive because their control electrodes are isolated from conductive devices, so they do not require continuous on-current. Once the MOSFET transistor is turned on, its drive current is almost zero
Also, the large reduction in control charge and correspondingly large reduction in MOSFET transistor storage time essentially eliminates the design trade-off between turn-on voltage drop and turn-off time, with the on-state voltage drop being inversely proportional to control charge. Thus, compared to bipolar devices, MOSFETs promise significant economic benefits using simpler and more efficient drive currents
In power applications, MOSFETs are resistive in nature, and the voltage drop across the drain-source terminal of the MOSFET is a linear function of the current flowing into the semiconductor. This linear relationship is characterized by the RDS(on) of the MOSFET, also known as the on-resistance
The on-resistance is constant for the gate-source voltage and the device temperature. Unlike the temperature coefficient of the p-n junction -2.2mV/°C, the temperature coefficient of the MOSFET is positive, about 0.7%/°C to 1%/°C
There are generally two types of MOSFETs:
Depletion type - when VGS=0, the channel is formed, and when the correct VGS is added, the majority of carriers can flow out of the channel, thus "depleting" the carriers and turning the tube to cut-off
Enhanced type——When VGS=0, the tube is in an off state. After adding the correct VGS, most carriers are attracted to the gate, thereby "enhancing" the carriers in this area and forming a conductive channel; Enhanced MOSFETs are divided into NPN type and PNP type
MOSFET is an insulated gate type, and its main feature is that there is a silicon dioxide insulating layer between the metal gate and the channel, so it has a very high input resistance (up to 1015Ω)
How MOSFETs work
The working principle of a MOSFET depends on the MOS capacitance, the semiconductor surface at the underlying oxide layer is located between the source and drain terminals, which can be reversed from p-type to n-type by applying a positive or negative gate voltage
When we apply a positive gate voltage, the holes under the oxide experience a repulsive force and the holes are pushed down by the substrate
The depletion region is filled with bound negative charges associated with the acceptor atoms, the electrons reach and form a 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 the source, the current flows freely between the source and the drain and the gate voltage controls the electrons in the channel. If a negative voltage is applied, a hole channel is formed under the oxide layer
P-channel MOSFET
A P-channel MOSFET has a P-channel region between the source and drain terminals, and it is a four-terminal device with terminals gate, drain, source, and body. The drain and source are heavily doped p + regions, the body or substrate is n-type, and the current flows in the direction of positive holes
When we apply a negative voltage with a repulsive force on the gate terminal, the electrons present under the oxide layer will be pushed down into the substrate. The depletion region consists of bound positive charges associated with the donor atoms. A negative gate voltage also attracts holes from the P+ source and drain regions into the channel region
N-channel MOSFET
An N-channel MOSFET has an N-channel region located between the source and drain terminals. It is a four terminal device with terminals gate, drain, source, body. In this field effect transistor, the drain and source are heavily doped n+ regions and the substrate or body is of P-type
Due to the current flow of negatively charged electrons in this type of MOSFET, when we apply a positive voltage with a repulsive force on the gate terminal, then the holes present under the oxide layer will be pushed down into the substrate. The bound negative charge associated with the acceptor atom in the depletion region constitutes
Upon arrival of electrons, a channel is formed, and the positive voltage also attracts electrons from the n+ source and drain regions into the channel. Now, if we apply a voltage between the drain and source, current will flow freely between the source and drain, while the gate voltage controls the electrons in the channel, if we apply a negative voltage, a hole channel will be formed under the oxide instead of a positive voltage
MOSFET Application
1. Power Amplifier - MOSFET can be used as a key component of a power amplifier to amplify electrical signals. Its high input impedance and low output impedance enable it to work at high frequencies while also being able to withstand high voltage and high current. This makes MOSFETs widely used in audio amplifiers, radio frequency amplifiers, power amplifiers, etc.
2. Switching circuit - MOSFET's high-speed switching characteristics make it an important component in switching circuits, and can be used in switching power supplies, motor drives, LED drive fields, etc. In these application scenarios, MOSFETs can quickly switch circuits for efficient power switching and control
3. Power management - MOSFET also has an important application in power management. It can realize high-efficiency conversion and protection of power supply, thereby ensuring the stability and reliability of the circuit. It is used in battery protection, power switch, power inverter and other fields
4. Analog switch - MOSFET can also be used as an analog switch. In the analog switch, it can realize the switching and adjustment of the circuit, so as to realize the precise control of the circuit. In audio, video and other fields, the analog switch of MOSFET is widely used
5. Sensors - MOSFETs can also be used in sensors, which can amplify and process sensor signals, thereby improving the sensitivity and accuracy of sensors. In the fields of temperature sensor signal, pressure sensor, photoelectric sensor, etc., MOSFET is widely used
MOSFET has a wide range of application scenarios in the electronic field. With the continuous development and progress of technology, its application scenarios will continue to increase
Who Manufacturers MOSFET?
1. Infineon Technologies - Infineon's N-channel and P-channel power MOSFETs are uniquely designed to bring higher efficiency, power density and cost-effectiveness
Infineon is the world's most well-known manufacturer of power semiconductor components, offering a comprehensive portfolio of metal oxide silicon transistors
2. STMicroelectronics - ST has ranked among the top MOSFET manufacturers in the world. Its power MOSFET product portfolio offers a wide range of breakdown voltages from -100 to 1700V, combining state-of-the-art packaging with low gate charge and low on-resistance. The company's process technology enhances power handling capabilities and ensures high-efficiency solutions through MDmesh high-voltage power MOSFETs and STripFET low-voltage power MOSFETs, ST power MOSFETs belong to the ST POWER series
3. Vishay - Vishay is one of the most important power MOSFET manufacturers in the world. The Vishay Siliconix MOSFET product line includes a variety of advanced technologies in more than 30 package types, from the chip-level MICRO FOOT and thermally advanced PowerPAK series to the classic "TO" transistor form factor
Single-die and multi-die MOSFETs feature integrated features such as Schottky diodes and ESD protection, while Vishay's unique PowerPAIR devices combine an optimized combination of MOSFETs for synchronous buck converters and other applications in a single package
4. Diodes Incorporated – The company provides MOSFETs needed for next-generation consumer, computer and communication product designs, enabling designers to optimize their end applications
Its broad MOSFET portfolio covers N-channel and P-channel voltage ranges from -450V to 800V in single, dual, complementary and H-bridge (quad) configuration packages
5. Nexperia – As a long-term supplier to the automotive industry, Nexperia maintains high-quality reliability standards with a broad portfolio of N and P-channel power MOSFETs ranging from 12V to 100V in space-saving and efficient packaging options, including its proven copper clip LEPAK technology
6. Renesas——Renesas Electronics provides power MOSFET products suitable for various applications such as power supply, motor drive, high-frequency amplification, and load switching. Its general-purpose power MOSFETs provide support for high-efficiency drive and low heat design. These MOSFETs are suitable for switching (motor drive, etc.) and load switching applications, and have low on-resistance, high-speed switching and high robustness
