FET Fundamentals Unit 2 – Junction FETS
UNIT 2 – JUNCTION FETS
UNIT OBJECTIVE
At the completion of this unit, you will be able to describe the operation of a junction field-effect
transistor (JFET) by using dc and ac measurements.
UNIT FUNDAMENTALS
A JFET has three terminals: gate (G), source (S), and drain (D).
JFETs are either N-channel or P-channel semiconductor devices.
The figure shows the proper bias for an N-channel JFET. JFETs are voltage-operated, current-
controlling devices. A reverse bias voltage, applied between the gate and source terminals,
produces a depletion region. The width of the depletion region, determined by the amount of
bias, controls the amount of current flow through the channel.