MOSFET is metal oxide field effect transistor. MOSFET is a voltage controlled device. MOSFET is majority carrier device. MOSFET are of two one is n-channel MOSFET and p-channel MOSFET. Gate, drain, and source are the three terminals of MOSFET. The current flows from drain to source when the voltage is applied between gate to the source terminal. The current between gate to source is very small. The active region, cutoff region, and ohmic region are the three regions in MOSFET. MOSFET goes in an ohmic region when the gate to source voltage is larger and drain to source voltage is small.
The ohmic region is also called as triode region. In the ohmic region, the MOSFET behaves like a small voltage controlled resistor. In the ohmic region, power dissipation is kept low by minimizing drain to source voltage even if the drain to source voltage is fairly large. Hence, power MOSFET is operated at high enough gate-source voltage to minimize the conduction losses.