Section 8: Keithley User Library Tool (KULT)
Model 4200A-SCS Parameter Analyzer Reference Manual
8-40
4200A-901-01 Rev. C / February 2017
Tutorial 4: Customizing a user test module (UTM)
This tutorial demonstrates how to modify a user module using KULT. In the
ivswitch
project, there
is a test named
rdson
. The
rdson
test measures the drain-to-source resistance of a saturated N-
channel MOSFET as follows:
1. Applies 2 V to the gate (V
g
) to saturate the MOSFET.
2. Applies 3 V to the drain (V
d1
) and performs a current measurement (I
d1
).
3. Applies 5 V to the drain (V
d2
) and performs another current measurement (I
d2
).
Calculates the drain-to-source resistance
rdson
as follows:
rdson
= (V
d2
-V
d1
) / (I
d2
-I
d1
)
The
rdson
test has a potential shortcoming. If the drain current is noisy, the two current
measurements may not be representative of the actual drain current. Therefore, the calculated
resistance may be incorrect.
In this example, the user module is modified in KULT so that ten current measurements are made at
V
d1
and ten more at V
d2
. The current readings at V
d1
are averaged to yield I
d1
, and the current
readings at V
d2
are averaged to yield I
d2
. Using averaged current readings smooths out the noise.
The modified test,
rdsonAvg
, measures the drain-to-source resistance of a saturated MOSFET. The
MOSFET is tested as follows when
rdsonAvg
is executed:
1. Applies 2 V to the gate (V
g
) to saturate the MOSFET.
2. Applies 3 V to the drain (V
d1
) and makes ten current measurements.
3. Averages the 10 current readings to yield a single reading (I
d1
).
4. Applies 5 V to the drain (V
d2
) and makes ten more current measurements.
5. Averages the ten current readings to yield a single reading (I
d2
).
6. Calculates the drain-to-source resistance (
rdsonAvg
) as follows:
rdsonAvg
= (V
d2
-V
d1
) / (I
d2
-I
d1
)
