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4.1 Introduction
FET tests discussed in this section include tests to generate
common-source characteristic curves, and transconductance
tests . Example programs for each of these applications are also
included .
4.2 Instrument Connections
Two SMU channels are required for the tests and a dual-channel
instrument from the Series 2600 System SourceMeter line is rec-
ommended . A test fixture with safety interlock is recommended
for connections to the FET under test .
For general-purpose measurements with most of the Series 2600
instruments, Model 2600-BAN cables are recommended . For low
current tests (<1mA) or when using a low current instrument like
the Model 2636, Model 7078-TRX-3 triax cables are recommended
to make instrument-to-test fixture connections .
WARNING
Lethal voltages may be exposed when the test fix-
ture lid is open. To avoid a possible shock hazard,
a safety interlock circuit must be connected before
use. Connect the fixture screw to safety earth
ground using #18 AWG minimum wire before use.
Turn off all power before connecting or discon-
necting wires or cables
Remote sensing connections are recommended for
optimum accuracy . See
If measurement noise is a problem, or for critical, low
level applications, use shielded cable for all signal
connections .
4.3 Common-Source
Characteristics
One of the more common FET tests involving family of curves
is common-source characteristics . Such tests are very similar to
the common-emitter characteristic tests outlined earlier except,
Section 4
NOTES
paragraph 1 .2 .2
for details .
FET Tests
of course, for the fact that an FET rather than a bipolar transistor
is involved .
Test data for common-source characteristics are obtained by
sweeping the gate-source voltage (V
values at specific increments . At each V
voltage (V
) is swept through the required range, once again at
DS
the desired increments . At each V
is measured . Plots can then be made from this data to show I
V
with one curve for each value of V
DS
4.3.1 Test Configuration
Figure 4-1 shows the test configuration for the common-source
tests . SMUB sweeps V
ment also measures I
signal, N-channel FET such as a SD210 is recommended .
4.3.2 example Program 9:
Common-Source Characteristics
Program 9 outlines general programming techniques for meas-
uring common-source characteristics . Follow these steps to use
this program:
1 .
With the power off, connect a dual-channel System Source-
Meter instrument to the computer's IEEE-488 interface .
2 .
Connect the test fixture to both units using appropriate
cables .
3 .
Turn on the instrument and allow the unit to warm up for two
hours for rated accuracy .
4 .
Turn on the computer and start Test Script Builder (TSB) . Once
the program has started, open a session by connecting to the
instrument . For details on how to use TSB, see the Series 2600
Reference Manual .
5 .
You can simply copy and paste the code from Appendix A in
this guide into the TSB script editing window
manually enter the code from the appendix, or import the TSP
file 'FET_Comm_Source.tsp' after downloading it to your PC .
If your computer is currently connected to the Internet, you
can click on this link to begin downloading:
keithley.com/data?asset=50921.
) across the desired range of
GS
value, the drain-source
GS
value, the drain current (I
DS
.
GS
, while SMUA sweeps V
, and the instru-
GS
DS
. For this programming example, a small-
D
)
D
vs .
D
(Program
9),
http://www.
4-1
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