Keithley 2651A Reference Manual page 72

Section 2: General operation
SourceMeter instrument configuration
Source voltage using series SMUs
2-50
Model 2651A High Power System SourceMeter® Instrument Reference Manual
HI
+
SMU 2
_
LO
LO
_
SMU 1
+
HI
Guidelines
Maximum Pulsed Signal Levels for Model 2651A:
80 V with 45 A compliance
SMU 1 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCVOLTS
Normal output-off current limit:
smuX.source.offlimiti = 1e-3 (default)
Current compliance must be 10% higher than the current compliance
of SMU 2. Current compliance limit (maximum):
smuX.trigger.source.limiti = 50
The polarity of SMU 1 is generally the opposite of the desired voltage
polarity across the device. In order to achieve a positive voltage
across the device, program SMU 1 to a negative voltage level. For
example, to output 80 V across the device, program SMU 1 to -40 V
and SMU 2 to +40 V. In order to achieve a negative voltage across the
device, program SMU 1 to a positive voltage level and SMU 2 to a
negative voltage level.
Source polarity changes incur a 100 μs penalty. The number 0 is
considered a positive value. For negative-going pulses with a 0 V bias
level, avoid the time penalty by programming a negative number very
near zero, for example, -1e-12 V.
SMU 2 configuration:
Output-off mode:
smuX.source.offmode = smuX.OUTPUT_NORMAL
Output-off function:
smuX.source.offfunc = smuX.OUTPUT_DCVOLTS
Normal output-off current limit (0.9 mA which is 10% less than the
SMU 1 smuX.source.offlimiti):
smuX.source.offlimiti = 0.9e-3
Current compliance must be 10% lower than the current compliance of
SMU 1.Therefore this SMU will control the maximum current through
the DUT. Current compliance limit (maximum):
smuX.trigger.source.limiti = 45
2651A-901-01 Rev. A / March 2011