MOSFET (Theory) : Digital VLSI Design

MOS transistor is a majority-carrier device, in which the current in a conducting channel between the source and the drain is modulated when we applied a voltage to the gate.

There are basically two types of MOS(Metal oxide semiconductor): N-mos & P-mos

NMOS (n-type MOS transistor)

Majority carrier = electrons

PMOS (p-type MOS transistor)

Majority carrier = holes

 Energy band diagram of MOS

There are three modes of operation of MOSFET

 Accumulation Region

• In this case, applied voltage (Vg) is less than flat band voltage or  The voltage applied to the gate(on the metal side) is negative.

Depletion Region

• In the depletion region, the voltage applied to the gate is greater than the flat band voltage and less than the threshold voltage.

Inversion Region:

• In the inversion region, the applied voltage is greater than the threshold voltage.

Why is MOS transistor used?

The MOSFET, short for Metal-Oxide-Semiconductor Field-Effect Transistor, is the most widely used type of transistor in modern electronics. Its main function is to regulate the flow of electricity between its source and drain terminals, depending on the voltage applied to its gate terminal.