Keithley 2657A User Manual

Model 2657A High Power System SourceMeter® Instrument Reference Manual Section 4: Theory of operation
2657A-901-01 Rev. B/December 2012 4-13
Load considerations (I-source)
The boundaries within which the High Power System SourceMeter
®
instrument operates depends on
the load (device-under-test (DUT)) that is connected to its output. The following figure shows
operation examples for resistive loads that are 5 kΩ and 20 kΩ, respectively. For these examples, the
System SourceMeter instrument is programmed to source 100 mA.
In the following figure (labeled "Normal I-source operation"), the System SourceMeter instrument is
programmed to limit voltage to 1000 V. The System SourceMeter instrument is sourcing 100 mA to
the 5 kΩ load and subsequently measures 500 V. As shown, the load line for 5 kΩ intersects the
100 mA current source line at 500 V. The voltage compliance limit is not reached (the instrument is
not limited through its compliance settings).
Figure 78: Normal I-source operation
The next figure (labeled "I-source operation in voltage compliance"), shows what happens if the
resistance of the load is increased to 20 kΩ. For this example, the System SourceMeter instrument is
programmed to limit voltage to 1000 V, with no other compliance limits. The DUT load line for 20 kΩ
intersects the voltage compliance limit line placing the System SourceMeter instrument in voltage
compliance. In compliance, the System SourceMeter instrument will not be able to source its
programmed current (100 mA). For the 20 kΩ DUT, the System SourceMeter instrument will only
output 50 mA (at the 1000 V limit).
Figure 79: I-source operation in voltage compliance
V-meter
(V
M
)
500 V
1000 V
100 mA
Programmed source value:
100 mA
Actual source value:
100 mA
V
V
10
10
10
10
0
0
0
0
m
mA
I-source
(I
S
)
Voltage
compliance
limit line
Programmed current
source value line
Operating
point
5
kΩ DUT
Load
Line (R)
V
M
= I
S
• R
= (100 mA) (5 kΩ)
= 500 V
o
a
n
R
)
V-meter
(V
M
)
500 V
1000 V
Voltage
compliance
limit line
Programmed current
source value line
100 mA50 mA
Programmed source value:
100 mA
Actual source value:
50 mA
I-source
(I
S
)
Operating
point
20 k
Ω D
UT Load
Lin
e
(
R
)
I
S
= V
M
/ R
= 1000 V / 20 kΩ
= 50 mA
U
T

Keithley 2657A Specifications

General

Brand	Keithley
Model	2657A
Category	Measuring Instruments
Language	English