Keithley 2600a series, Reference Manual, Page: 116 / 696

4-22 Return to Section Topics 2600AS-901-01 Rev. B / September 2008
Section 4: Source-Measure Concepts Series 2600A System SourceMeter® Instruments Reference Manual
This filter is only active when the amps measure range is 1nA/100pA. Setting the attribute to zero
disables the filter.
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.
Table 4-5 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 60kHz 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 4-5 .
Table 4-5
Current source gain-bandwidth
Range
SMU feedback
impedance 60kHz ratio
(DUT / SMU impedance)
Minimum DUT
impedance
1nA 1G
Ω
0.5 2G
Ω
10nA 120M
Ω
0.5 60M
Ω
100nA 40M
Ω
0.5 20M
Ω
1
μ
A 1.2M
Ω
0.5 600k
Ω
10
μ
A 400k
Ω
0.5 200k
Ω
100
μ
A 12k
Ω
0.5 6k
Ω
1mA 4k
Ω
0.5 2k
Ω
10mA 120
Ω
0.5 60
Ω
100mA 40
Ω
0.5 20
Ω
1A 1
Ω
6 6
Ω
1.5A 1
Ω
6 6
Ω
3A 0.3
Ω
5 1.5
Ω