JFET - Junction field effect transistors

JFET

Junction field effect transistors like BJTs are three lead

semiconductor devices.

• JFETs are used as:

– electrically controlled switches,

– current amplifiers, and

– voltage-controlled resistors.

Unlike BJTs, JFETs do not require a bias current and are controlled

by using only a voltage.

JFETs are normally on when VG - VS = 0.

When VG - VS z 0, then JFETs become resistive to current flow

through the drain-source pair o “JFETs are depletion devices