Figure 6-13 V-Source Limit Lines; Figure 6-16 Source; Current Compliance Boundaries - Keithley SourceMeter 2400 User Manual

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6-28 Source-Measure Concepts 2400 Series SourceMeter User's Manual
Figure 6-13 shows the limit lines for the V-Source. The voltage source limit line represents
the maximum source value possible for the presently selected voltage source range. For
example, if on the 20V source range, the voltage source limit line is at 21V. The current
compliance limit line represents the actual compliance in effect. Remember that compli-
ance can be real or range. (See "Compliance limit," page 6-2.) These limit lines are bound-
aries that represent the operating limits of the SourceMeter for this quadrant of operation.
The operating point can be anywhere inside (or on) these limit lines. The limit line bound-
aries for the other quadrants are similar.
Figure 6-13
V-Source limit lines
Current Compliance
Limit Line
I Measure
Voltage Source
Limit Line
V Source

Current compliance boundaries

Where within the boundaries the SourceMeter operates depends on the load (DUT) that is
connected to the output. Figure 6-14 shows operation examples for resistive loads that are
2kΩ and 800Ω, respectively. For these examples, the SourceMeter is programmed to
source 50V and limit 50mA.
In Figure 6-14A, the SourceMeter is sourcing 100V to the 2kΩ load and subsequently
measures 25mA. As shown, the load line for 2kΩ intersects the 50V voltage source line at
25mA.
Figure 6-14B shows what happens if the resistance of the load is decreased to 800Ω. The
DUT load line for 800kΩ intersects the current compliance limit line placing the
SourceMeter in compliance. In compliance, the SourceMeter will not be able to source its
programmed voltage (50V). For the 800kΩ DUT, the SourceMeter will only output 40V
(at the 50mA limit).
Notice that as resistance decreases, the slope of the DUT load line increases. As resistance
approaches infinity (open output), the SourceMeter will source virtually 50V at 0mA.
Conversely, as resistance increases, the slope of the DUT load line decreases. At zero
resistance (shorted output), the SourceMeter will source virtually 0V at 50mA.
Regardless of the load, current will never exceed the programmed compliance of 50mA.
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