JUNCTION FIELD EFFECT TRANSISTOR ( FJT)

Junction Field Effect Transistor (JFET)
❑ JFET is made of a channel (p-channel or n-
channel)
Drain (D)
Drain (D)




p-channel
Gate Gate
p-channel




(G)
n n (G)



Source (S)
Source (S)
p-channel JFET

Department of EE

,Junction Field Effect Transistor (JFET)
❑ Basic structure of two types of JFET (n-channel
and p-channel)
Drain (D) Drain (D)




p-channel
n-channel
Gate Gate Gate
Gate n n (G)
(G) p p (G) (G)



Source (S) Source (S)

n-channel JFET p-channel JFET
Department of EE

,Junction Field Effect Transistor (JFET)…..
❑ The main body of the transistor is the conducting
channel made of either n-type or p-type
semiconductors to give n-channel JFET or p-
channel JFET respectively
❑ The JFET uses only one type of carriers for
conduction. Hence it is known as Unipolar (one
polarity) transistors (either holes or Electrons)
❑ The leads are named Source, Gate and Drain


Department of EE

, Junction Field Effect Transistor (JFET)…..
❑ The JFET is always operated with the gate-source
pn junction reverse biased
❑ This produces depletion layer between the gate
and the channel
❑ The conducting channel width can be controlled
by depletion layer
❑ Therefore JFET operates in the Depletion mode
by the control voltage at the gate

Department of EE