Q.Expand MOSFET.

The power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a voltage-controlled power device. The current between its two main terminals — the drain (D) and the source (S) — is controlled by the voltage on an insulated gate (G) that is separated from the semiconductor body by a thin metal-oxide layer. The gate voltage sets up an electric field that modulates the conductivity of the channel between drain and source; because the gate is insulated, it draws almost no steady current, giving the MOSFET a very high input impedance.

Enhancement-type power MOSFETs come in two kinds, n-channel and p-channel. In the symbol, a broken (segmented) channel line marks the enhancement (normally-off) type, and the direction of the body arrow distinguishes n-channel from p-channel.

The output characteristics plot drain current $I_D$ against drain-source voltage $V_{DS}$, with the gate-source voltage $V_{GS}$ held constant for each curve. Three modes appear: …