Keithley 2635 Reference Manual

8-12 Return to Section Topics 2600S-901-01 Rev. C / January 2008
Section 8: Source-Measure Concepts Series 2600 System SourceMeter® Instruments Reference Manual
Load considerations
The boundaries the SourceMeter operates in depends on the load (DUT) that is connected to its
output.
Figure 8-7 shows operation examples for resistive loads that are 50Ω and 200Ω,
respectively. For these examples, the SourceMeter is programmed to source 100mA and limit 10V.
In Figure 8-7A, the SourceMeter is sourcing 100mA to the 50Ω load and subsequently measures
5V. As shown, the load line for 50Ω intersects the 100mA current source line at 5V.
Figure 8-7B shows what happens if the resistance of the load is increased to 200Ω. The DUT load
line for 200Ω intersects the voltage compliance limit line placing the SourceMeter in compliance. In
compliance, the SourceMeter will not be able to source its programmed current (100mA). For the
200Ω DUT, the SourceMeter will only output 50mA (at the 10V limit).
Notice that as resistance increases, the slope of the DUT load line increases. As resistance
approaches infinity (open output), the SourceMeter will source virtually 0mA at 10V. Conversely,
as resistance decreases, the slope of the DUT load line decreases. At zero resistance (shorted
output), the SourceMeter will source 100mA at virtually 0V.
Regardless of the load, voltage will never exceed the programmed compliance
of 10V.
Figure 8-7
I-Source operating examples
Voltage Limit
Load Line
Operating
Point
Current Source
Load Line
I-Source (I
S
)
I-Source (I
S
)
V-Meter
(V
M
)
V-Meter
(V
M
)
5V
10V
100mA
50W DUT Load Line (R)
A) Normal I-source operation
Voltage Limit
Load Line
Operating
Point
Current Source
Load Line
10V
100mA
B) I-source in compliance
50mA
200W DUT Load Line (R)
V-Meter = I
S
 R
= (100mA) (50W)
= 5V
I
S
= V
M
/ R
= 10V / 200W
= 50mA

Keithley 2635 Specifications

General

Brand	Keithley
Model	2635
Category	Measuring Instruments
Language	English