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 0, then JFETs become resistive to current flow
through the drain-source pair “JFETs are depletion devices.