•
Measurements are conducted in
pulsed mode
. That is, the measurement conditions are applied to the device
under test for a brief interval. The hardware captures the device behaviour during the measurement interval.
The measurement conditions are then removed, allowing the device and the driver electronics to cool. This
approach minimizes the size and cost of the hardware, and allows measurements of a semiconductor device
up to and beyond its rated values.
For example, light emitting diodes are often operated in pulsed mode at peak currents well in excess of their
maximum allowable continuous current. The CTR-201 can take pulsed measurements up to a maximum of
1 ampere forward current.
The interval between measurements automatically increases at higher currents to control the power dissipa-
tion in the device.
•
Legacy instruments provided a repeditive display of the measurement curve. In the CTR-201, data is
captured in one measurement sweep, minimizing the dissipation in the device under test.
•
Legacy instruments often used dissipation limiting resistors in series with the device under test. Then, as
the current was increased in the device, the voltage across the device decreased. This was a useful approach
to protect the device under test
2
. However, it limited the measurement at the corner values of voltage and
current. You could measure the device at maximum voltage or current, but not both at once.
The CTR-201 contains no dissipation limiting resistances, and the current sensing resistances are small. As
a result, the device can be tested at the full limit of the curve tracer capabilities - about 35 volts at 1 ampere.
•
Legacy instruments typically provide voltage-current curves. A computer-based instrument like the CTR-
201 can provide many more modes of display and analysis, such as the variation in current gain of a BJT
over a range of operating currents, or the incremental collector resistance as a function of collector voltage.
The data can be captured and transferred to a spreadsheet or other program for further analysis.
•
Because the CTR-201 hardware is hosted by a computer it is straightforward to capture screen shots, save
the data to a file for further analysis, or project the screen image in a teaching environment.
2
As well, the voltage across the dissipation resistance could be used as a measurement of the current through the device.
3
