Technical data

Application Examples 5
U1401A User’s and Service Guide 105
You can identify the channel type of a JFET by measuring
its drain- source resistance (R
DS
) when it is biased with a
constant voltage source. Usually, both channel types will
switch on under a gate- source voltage (V
GS
) of 0 V.
5 Connect the red input probe lead to the drain.
6 Connect the black input probe lead to the source.
7 Connect the red output alligator lead to the gate terminal
through a 100 kΩ resistor, and connect the black output
alligator lead to the black input probe lead.
If R
DS
increases when V
GS
is a negative value, then it is an
n- channel JFET. On the other hand, if R
DS
increases when
V
GS
is a positive value, then it is a p- channel JFET.
Table 5 - 7 Gate terminal according to probe test
Pins Test l ea d s Gate
Red/Black Black/Red
1-2 <1 kΩ <1 kΩ 3
1-3 <1 kΩ <1 kΩ 2
2-3 <1 kΩ <1 kΩ 1