Diode Test Example - Keithley SourceMeter 2400 User Manual

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10-12 Sweep Operation 2400 Series SourceMeter User's Manual

Diode test example

Limit testing and a source memory sweep can be used to test a diode. Three tests that are
typically performed on a diode include the Forward Voltage Test (V ), Reverse Break-
F
down Voltage Test (V and Leakage Current Test (I ). Figure 10-6 illustrates the test
R) R
points on a typical diode curve.
Figure 10-6
Typical diode I-V curve and test points (not to scale)
I
V Test
F
-V V
I Test
R
V Test
R
-I
Forward Voltage Test (V — This test involves sourcing a specified forward bias current
F)
within the normal operating range of the diode, then measuring the resulting voltage drop.
To pass the test, the voltage must be within the specified minimum and maximum values.
Reverse Breakdown Test (V ) — A specified reverse current bias is sourced and the
R
resulting voltage drop across the diode is measured. The voltage reading is compared to a
specified minimum limit to determine the pass/fail status of the test.
Leakage Current Test (I ) — The leakage test verifies the low level of current that leaks
R
across the diode under reverse voltage conditions. A specified reverse voltage is sourced,
then the resultant leakage current is measured. Good diodes have leakage current that is
less than or equal to the specified maximum value.
This test example also uses sweep branching to simplify handling of each diode. No mat-
ter how the polarity sensitive diode is installed in the test fixture, it will be biased properly.
See "Sweep branching" for details.
Testing process — The test uses seven SMLs (source memory locations). However, only
four memory locations are used for each tested diode. If the diode is installed correctly,
tests at locations 001, 002, 003, and 004 are performed. If the diode is installed backwards,
tests at locations 001, 005, 006, and 007 are performed. To sweep four memory locations,
the sweep count must be set to four. The source memory sweep is summarized as follows:
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