Keithley 7174A, Инструкция по эксплуатации

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Applications
3-6
3.3.2 Testing common-source characteristic of
FETs
The system shown in Figure 3-5 could be used to test a vari-
ety of characteristics including I
GSS
, I
D[OFF]
, I
G[ON]
, I
DSS
,
and V
DS[OFF]
. To demonstrate a practical use for the system,
we will show how it can be used to generate common source
characteristic curves of a particular JFET.
In order to generate these curves, the instrument must be
connected to the JFET under test, as shown in Figure 3-6.
The advantage of using the matrix is, of course, that it is a
simple matter of closing specific crosspoints. The cross-
points that must be closed are also indicated on the diagram.
To run the test, V
GS
is set to specific values, for example in
increments of 0.25V. At each V
GS
value, the drain-source
voltage (V
DS
) is stepped across the desired range, and the
drain current, I
D
, is measured at each value of V
DS
. Once all
data are compiled, it is a simple matter to generate the
common-source IV curves, an example of which is shown in
Figure 3-7. If the system is connected to a computer, the test
and graphing could all be done automatically.
D
G
V
DS
V
GS
I
D
= Closed Crosspoints on 7174A Card (Figure 3-5).
Model 230
Voltage Source
617
Electrometer/Source
Meter
(Current)
Voltage
Source HI
HI
HI
LO
LO
LO
C11
D9
B9
A12
F8 F10
E9
E11
S
Figure 3-6
System configuration for measuring common-emitter characteristics
10 0
9 0
8 0
7 0
6 0
5 0
4 0
3 0
2 0
0
0 2 3 4 5 6 7 8 9
10
1
1 0
V = 0V
GS
V = -0.5V
GS
V = -1V
GS
V (Volts)
DS
I
D
(
µ
A)
Figure 3-7
Typical common-source FET IV characteristics
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