MOSFET is an acronym for “metal–oxide–semiconductor field-effect transistor,” which is an important element in embedded system design that is utilized to control the loads as per a user’s requirements. Many electronic projects such as light intensity control, motor control, and max generator applications take advantage of the MOSFET. Additionally, the MOSFET provides key features for circuit designers in terms of overall performance.

Considered a semiconductor device, the MOSFET is popularly used for switching and amplifying electronic signals in a wide range of electronics. It contains three terminals: source, gate, and drain ports. It works by varying the width of a channel where electrons flow. The electrons make their way into the channel from the source and exit via the drain.

Meanwhile, the channel width is typically controlled by the voltage on the gate, which lies between the source and drain. It is insulated from the nearby channel with an extremely thin layer of metal oxide. According to the user’s needs, MOSFET devices can be classified as either depletion mode MOSFET or enhancement mode MOSFET.

Depletion Mode MOSFET

When there is zero voltage on the gate terminal, the channel displays its maximum conductance. Whether the voltage on the gate is negative or positive, the channel conductivity always decreases.

Enhancement Mode MOSFET

When no voltage is present on the gate terminal, the device does not conduct. If more voltage is applied on the gate terminal, the device provides good conductivity.

Working of a MOSFET

The metal oxide capacitor is the main part of the MOSFET and determines how well it works. In addition, the source and drain terminals can be set from p-type to n-type by applying positive or negative gate voltages on each, and they are usually encapsulated with an oxide layer. When applying the positive gate voltage, the holes present under the oxide layer are pushed downward through the substrate. Furthermore, the deflection region is replete with bound negative chargers which are allied with acceptor atoms.

P-Channel MOSFET

P-Channel MOSFET contains negative ions and works with negative voltages. When a negative voltage is applied to the gate, electrons under the oxide layer are pushed downward into the substrate with ample force. The deflection region is populated by the bound positive charges which are allied with donor atoms. Finally, the negative voltage attracts holes from the p+ source and drain region into the channel region.

N-Channel MOSFET

As previously mentioned, when the positive gate voltage is applied, the holes under the oxide layer are pushed downward into the substrate with great force. The deflection region is populated by the bound negative charges that are allied with acceptor atoms. The positive voltages attract electrons from the n+ source and drain regions into the channel. If the voltage applied to the drain and source, current flows freely between the source and drain, and the gate voltage controls the electrons in the channel. If a negative voltage is applied, the channel will be formed under the oxide layer.


The MOSFET finds use in an array of applications such as electrical and electronic projects. For instance, the MOSFET is used as a switch for LEDs and lamps. Other lighting systems also take advantage of the MOSFET, including the auto intensity control of street lights.


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December 6, 2021

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