MOSFET | Working Principle of p-channel n-channel MOSFET
MOSFET stands for metal oxide semiconductor field effect transistor. It is capable of voltage gain and signal power gain. The MOSFET is the core of integrated circuit designed as thousands of these can be fabricated in a single chip because of its very small size. Every modern electronic system consists of VLST technology and without MOSFET, large scale integration is impossible.
It is a four terminals device. The drain and source terminals are connected to the heavily doped regions. The gate terminal is connected top on the oxide layer and the substrate or body terminal is connected to the intrinsic semiconductor.
MOSFET has four terminals which is already stated above, they are gate, source drain and substrate or body. MOS capacity present in the device is the main part. The conduction and valance bands are position relative to the Fermi level at the surface is a function of MOS capacitor voltage. The metal of the gate terminal and the sc acts the parallel and the oxide layer acts as insulator of the state MOS capacitor. Between the drain and source terminal inversion layer is formed and due to the flow of carriers in it, the current flows in MOSFET the inversion layer is properties are controlled by gate voltage. Thus it is a voltage controlled device. Two basic types of MOSFET are n channel and p channel MOSFETs. In n channel MOSFET is current is due to the flow of electrons in inversion layer and in p channel current is due to the flow of holes.
Another type of characteristics of clarification can be made of those are enhancement type and depletion type MOSFETs. In enhancement mode, these are normally off and turned on by applying gate voltage. The opposite phenomenon happens in depletion type MOSFETs.
Working Principle of MOSFETThe working principle of MOSFET depends up on the MOS capacitor. The MOS capacitor is the main part. The semiconductor surface at below the oxide layer and between the drain and source terminal can be inverted from p-type to n-type by applying a positive or negative gate voltages respectively. When we apply positive gate voltage the holes present beneath the oxide layer experience repulsive force and the holes are pushed downward with the substrate. The depletion region is populated by the bound negative charges, which are associated with the acceptor atoms. The positive voltage also attracts electrons from the n+ source and drain regions in to the channel. The electron reach channel is formed.
Now, if a voltage is applied between the source and the drain, current flows freely between the source and drain gate voltage controls the electrons concentration the channel. Instead of positive if apply negative voltage a hole channel will be formed beneath the oxide layer. Now, the controlling of source to gate voltage is responsible for the conduction of current between source and the drain. If the gate voltage exceeds a given value, called the three voltage only then the conduction begins. The current equation of MOSFET in triode region is - Where, un = Mobility of the electrons Cox = Capacitance of the oxide layer W = Width of the gate area L = Length of the channel VGS = Gate to Source voltage VTH = Threshold voltage VDS = Drain to Source voltage.