Section 3: Source-measure hardware
Model 4200A-SCS Parameter Analyzer Reference Manual
3-4
4200A-901-01 Rev. C / February 2017
If you set a specific measurement range, compliance can also be restricted by the range. Compliance
must be more than 11% of the measurement range. If not, an event is generated and the compliance
setting is automatically changed to the maximum compliance value for the selected range. For
example, if compliance is set to 1 V and the measurement range is 200 mV, output voltage will clamp
at 210 mV. If you attempt to change compliance to a value that is not appropriate for the selected
range, compliance is not changed and a warning is generated. You must change the range before
you can select the new compliance value. If you set the measurement range to be automatically
selected, the measurement range does not affect compliance.
The lowest allowable compliance is based on the load and the source value. For example, if you are
sourcing 1 V to a 1
kΩ resistor, the lowest allowable current compliance is 1 mA (1 V/1 kΩ = 1 mA).
Setting a compliance lower than 1 mA limits the source.
For another example, assume the following conditions:
•
Current compliance: 10 mA
•
Voltage sourced by the instrument: 10 V
•
DUT resistance: 10 Ω
With a source v
oltage of 10 V and a DUT resistance of 10 Ω, the current through the DUT should be
10 V / 10
Ω = 1 A. However, because compliance is set to 10 mA, the current cannot exceed 10 mA,
and the voltage across the resistance is limited to 100 mV. In effect, the 10 V voltage source is
transformed into a 10 mA current source.
In steady-state conditions, the set compliance value restricts the instrument output unless there are
fast transient load conditions.
When measurement autorange is disabled, the maximum and minimum compliance values cannot be
set below the minimum value. When autorange is enabled, the programmed compliance value cannot
be set below 10 nA when sourcing voltage, or below 20 mV when sourcing current.
Source or sink
Depending on how they are programmed and what is connected to the output (load or source), the
SMUs can operate in any of the four quadrants. The four quadrants of operation for the 4200-SMU
and 4210-SMU are shown in the next figures. When operating in the first (I) or third (III) quadrant, the
SMUs are operating as a source (V and I have the same polarity). As a source, the SMUs are
delivering power to a load. When operating in the second (II) or fourth (IV) quadrant, the SMUs are
operating as a sink (V and I have opposite polarity). As a sink, they are dissipating power rather than
sourcing it.
