8-34 Source-Measure Concepts Series 2600 System SourceMeters Reference Manual
2600S-901-01 Rev. A / May 2006 Return to Section 8 topics
Settling time considerations
Reduction in gain-bandwidth
The settling time of the SMU can be influenced by the impedance of the DUT in
several ways. One influence is caused by an interaction between the impedances
of the SMU current source feedback element and the DUT. This interaction can
cause a reduction in gain-bandwidth. When the SMU gain-bandwidth is reduced,
the settling time of the current source increases.
The settling times listed in the specifications found in Appendix A assume that the
gain-bandwidth of the SMU is approximately 60 kHz. Table 8-2 below can be used
to determine the affect of various DUT impedances on the gain-bandwidth when
the SMU is operating on each current source range. If the ratio of DUT impedance
to current source feedback impedance drops below the indicated 60 kHz ratio,
then the settling time will increase beyond the specified times. Therefore, there is
a minimum DUT impedance for each current source range. The settling time on a
current range can increase significantly when measuring DUTs that have an
impedance that is lower than that listed in
Table 8-2 below.
Table 8-2
Current source gain-bandwidth
Range
SMU feedback
impedance
60kHz ratio
(DUT / SMU impedance)
Minimum DUT
impedance
100nA 40MΩ 0.5 20MΩ
1μA 1.2MΩ 0.5 600kΩ
10μA 400kΩ 0.5 200kΩ
100μA 12kΩ 0.5 6kΩ
1mA 4kΩ 0.5 2kΩ
10mA 120Ω 0.5 60Ω
100mA 40Ω 0.5 20Ω
1A 1Ω 6 6Ω
1.5A 1Ω 6 6Ω
3A 0.3Ω 5 1.5Ω
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