What is MOSFET?
What is MOSFET?
A metal-oxide-semiconductor field-effect transistor (MOSFET, MOS-FET or MOS FET) is a field-effect transistor (FET with an insulated gate) where the voltage determines the conductivity of the device. It is used for switching or amplifying signals. The ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. MOSFETs are now even more common than BJTs (bipolar junction transistors) in digital and analog circuits.
A MOSFET is by far the most common transistor in digital circuits, as hundreds of thousands or millions of them may be included in a memory chip or microprocessor. Since they can be made with either p-type or n-type semiconductors, complementary pairs of MOS transistors can be used to make switching circuits with very low power consumption, in the form of CMOS logic.
MOSFET Operation
The purpose of the MOSFET is to be able to monitor the voltage and current flow between the source and the drain. It acts more like a tap. The function of MOSFET relies on the MOS capacitor. The core component of MOSFET is the MOS capacitor. The semiconductor surface below the oxide layer situated between the source and the drain terminal. It can be inverted from p-type to n-type by applying positive or negative gate voltages. When the positive gate voltage is applied, the holes under the oxide layer with repulsive force and the holes are pushed down with the substrate. The depletion area is filled by bound negative charges correlated with the acceptor atoms. The electrons are created to enter the tube. Positive voltage often absorbs electrons from the n+ source and flows into the tube. Currently, as a voltage is applied between the drain and the outlet, the current flows freely between the source and the drain and the gate voltage regulates the electrons in the pipe. Instead of a positive voltage, if we add a negative voltage, avoid the canal would be created under the oxide sheet.
MOSFET Types
The MOSFET is classified into two types such as:
- Depletion mode MOSFET
- Enhancement mode MOSFET
Depletion Mode: When there is zero voltage on the gate terminal, the channel shows its maximum conductance. As the voltage on the gate is negative or positive, then decreases the channel conductivity.
Enhancement Mode: When there is no voltage on the gate terminal the device does not conduct. More voltage applied to the gate terminal; the device has good conductivity.
P-Channel MOSFET
The P-MOSFET channel has a P-Channel area between the source and the drain. It's a four-terminal device, like a gate, a drain, a source or a body. The drain and the source are heavily doped in the p+ region and the body or substrate is n-type. The present flow is strongly lined with gaps. As the negative gate voltage is applied, the electrons present under the oxide layer are forced down into the substrate with a repulsive force. The depletion region is populated by bound positive charges associated with donor atoms. Negative gate voltage often draws holes from the p+ source and drains into the channel field.
N- Channel MOSFET
The N-Channel MOSFET has an N-Channel area between the source and the drain This is a four-terminal system, such as the wall, drain, spring or core. This form of MOSFET drain and source is a highly doped n+ area and the substrate or structure is P-scale. Present flows are attributable to negatively charged electrons. Once the positive gate voltage is applied, the holes under the oxide layer are forced back into the ground with repulsive force. The depletion area is filled by bound negative charges correlated with the acceptor atoms. The electrons are created to enter the tube. Positive voltage often absorbs electrons from the n+ source and flows into the tube. Currently, as a voltage is applied between the drain and the outlet, the current passes freely between the outlet and the drain and the gate voltage regulates the electrons in the pipe. Because of positive voltage, if we add negative voltage, the void channel would be created under the oxide sheet.
- MOSFET amplifiers are extensively used in radio frequency applications.
- It acts as a passive element like resistor, capacitor, and inductor.
- DC motors can be regulated by power MOSFETs.
- The high switching speed of MOSFETs makes it an ideal choice in designing chopper circuits.
- MOSFETs provide greater efficiency while operating at lower voltages.
- Absence of gate current results in high input impedance producing high switching speed.
- They operate at lower power and draw no current.
- The thin oxide layer makes the MOSFETs vulnerable to permanent damage when evoked by electrostatic charges.
- Overload voltages make it unstable.