Field Effect Transistor

In a field effect transistor, the input voltage controls the output current. The input current is extremely small, < 1 pA.

There are two main classes of FETs:

JFET Junction FET

MOSFET Metal Oxide

Semiconductor FET

“Field effect” is so-called because an electric field is used to control current. As we shall see, the transistor current only depends on the movement of one type of mobile charge carrier and is often termed a “unipolar” device.