Keithley SourceMeter 2600 Series Reference Manual page 240

8-34 Source-Measure Concepts
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
gain-bandwidth of the SMU is approximately 60 kHz.
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
Current source gain-bandwidth
Range
100nA
1μA
10μA
100μA
1mA
10mA
100mA
1A
1.5A
3A
2600S-901-01 Rev. A / May 2006
Series 2600 System SourceMeters Reference Manual
SMU feedback
impedance (DUT / SMU impedance)
40MΩ
1.2MΩ
400kΩ
12kΩ
4kΩ
120Ω
40Ω
1Ω
1Ω
0.3Ω
Return to Section 8 topics
Appendix A
Table 8-2
Table 8-2 below.
60kHz ratio
0.5
0.5
0.5
0.5
0.5
0.5
0.5
6
6
5
assume that the
below can be used
Minimum DUT
impedance
20MΩ
600kΩ
200kΩ
6kΩ
2kΩ
60Ω
20Ω
6Ω
6Ω
1.5Ω