Q. What are the different types of MOSFET transistors ?

The metal-oxide semiconductor field-effect transistor (MOSFET) is a three-terminal active device which has many applications in both analog and digital electronics. The three terminals are the source (S), the drain (D), and the gate (G). The gate is insulated from the channel, which permits the gate-to-source voltage to be either positive or negative without the flow of gate current for both the n-channel and the p-channel devices.

There are two types of MOSFET's: the depletion mode device and the enhancement mode device. In each, the current which flows in the drain-to-source channel is a function of the voltage applied from gate to source. In the depletion mode device, the channel is conducting when the gate-to-source voltage is zero. In contrast, in the enhancement mode device, the channel is non-conducting when the gate-to-source voltage is zero. For enhancement mode devices, the drain current is zero until the gate-to-source voltage exceeds a value that is known as the threshold voltage (Vt).

There are n-channel and p-channel type MOSFET transistor

A p-channel MOSFET (PMOS) transistor is fabricated on an n-type substrate with p+ regions for the drain and source, and holes as charge carriers.

A n-channel MOSFET (NMOS) transistor is fabricated on an p-type substrate with n- regions for the drain and source, and electrons as charge carriers.