Section 5: Source-measure concepts
Model 4200A-SCS Source-Measure Unit (SMU) User's Manual
5-20
4200A-SMU-900-01 Rev. A December 2020
Source-delay-measure cycle
During each source-delay-measure cycle, the following occurs:
1. The source output level is set.
2. There is a wait for the source delay.
3. The measurement is made.
The delay phase of the cycle, which is programmed by software, allows the source and external
circuitry to settle before the measurement is made. Although the source settles quickly if unit is not in
compliance, external voltage or current settling may take longer due to interaction between the DUT
and the SMU.
When there is more capacitance at the output, more settling time is required for the source signal.
The actual delay that is needed can be calculated or determined by trial and error. For purely resistive
loads and at higher current levels, the sweep delay can be set to a minimum.
The measure time depends on the selected integration period and it can be extended by autorange.
Figure 93: Source-measure-delay cycle
Sweep waveforms
The general sweep types are linear staircase, logarithmic staircase, multi-segment, and custom, as
shown in the following figure. The linear staircase sweep goes from the start level to the stop level in
equal linear steps. The logarithmic staircase sweep is similar, except it is done on a logarithmic scale
with a specified number of steps per decade. The multisegment sweep increments through a series of
segments with variable voltage or current steps. The custom sweep lets you construct your own
sweep by specifying the number of measure points and the source level at each point.
