What is MOSFET – Working, Types, Applications, Advantages & Disadvantages

What is MOSFET

Metal oxide silicon Field impact electronic transistor is abbreviated as MOSFET. It is just a unipolar electronic transistor AN used as an electronic switch and to amplify electronic signals. The device has 3 terminals consisting of a supply, gate and drain. Apart from these terminals there's a substrate usually known as the body that is usually connected to the supply terminal for sensible applications.

In recent years, its discovery has led to the dominant usage of those devices in digital integrated circuits because of its structure. The Silicon di-oxide (SiO2) layer acts as an insulator and provides electrical isolation between the gate and an active channel between the source and the drain which provides high input electrical resistance that is sort of infinite so capturing all the signal.

Working Principle of MOSFET

It is fabricated by the oxidation of silicon substrates. It works by altering the width of the channel through which the movement of charge carriers (electrons for N-channel and holes for P-channel) occurs from source to drain. The gate terminal is insulated whose voltage regulates the conduction of the device.

Applications of MOSFET

MOSFET amplifiers ar extensively utilized in radio frequency applications.

It acts as a passive part like electrical device, capacitor and inductor.

DC motors can be regulated by power MOSFETs.

High switching speed of MOSFETs make it an ideal choice in designing chopper circuits.

Types of MOSFET

On the basis of Operational Mode, MOSFETs can be classified into two types.

•          Enhancement Type MOSFETs

•          Depletion Type MOSFETs

Enhancement Type MOSFET

In this mode, there's no conductivity at zero voltage which suggests it's closed or “OFF” by default as there's no existing channel. When the gate voltage is increased over the supply voltage, the charge carriers (holes) shifts away leaving behind the electrons and thus a wider channel is established.

The gate voltage is directly proportional to the present i.e. as the gate voltage increases the current increases and vice versa.

Depletion Type MOSFET

In this sort, the channel is already established and it is evident that the conduction occurs even at zero voltage and it is open or “ON” by default. Unlike improvement sort, here the channel is depleted of charge carriers to reduce the width of the channel.

The gate voltage is reciprocally proportional to the present i.e. as the gate voltage increases the current decreases.

Advantages of MOSFET

• MOSFETs provide excellent 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 draws no current.

Disadvantages of MOSFET                             

• The thin oxide layer make the MOSFETs vulnerable to permanent damage when evoked by

              electrostatic charges.

• Overload voltages makes it unstable.