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APPLICATIONS
Model
617 Electrometer/Source:
Measures current,
and
also could be used to measure voltages up to GIOOVDC.
The DC voltage source can supply a maximum
of +lOOV
at currents up to 21~4.
Model
230 Voltage Source: Sources DC voltages up to
*lOlV
at a maximum
current of lOOmA.
Model 590 CV Analyzer:
Adds CV sweep measurement
capability
to the system.
Model 220 Current Source: Used to source currents up to
a maxinwm
of 1OlmA with a maximum compliance voltage
of 105V.
Model
196 DMM:
Measure DC voltages in the range of
1OOnV to 300V. The Model
196 could also be used to
measure resistance in certain applications.
Device Under Test: A three-terminal
fiitwe
for testing such
devices as bipolar transistors and FETs. Additional
connec-
tions could easily be added to test more complex devices,
as required.
3.3.2 Testing Common-Source
Characteristic
of FETs
The system shown in Figure 3-5 could be used to test a
variety of characteristics
including
I ass, Lqm,,
L,m,, Ls,
and Vos,,,,. 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 instruments
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
crosspoints that must be closed are also indicated on the
diagram.
To run the test, V,, is set to specific specific values, for
example in increments
of 0.25V. At each V,, value, the
drain-source
voltage (V,,) is stepped across the desired
range, and the drain current, I,, is measured at each value
of V,
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
617
Electrometer/Source
@=
Closed Crosspoints
on 7072 Card (Figure 3-5).
Figure 3-6. System Configuration
for Measurlng Common-Emitter
Characteristics
3-8
I
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