Table 8-5 Current Source Gain-Bandwidth; Reduction In Gain-Bandwidth - Keithley 2601 Reference Manual

Section 8: Source-Measure Concepts
increasing the delay factor to 1.3 will account for settling to 0.01% of the final value. The
commands to manipulate the delay factor and analog filter are shown below:
For controlling settling time
smuX.measure.delay = 0
smuX.measure.delay = Y
smuX.measure.delayfactor = 1.0
This factor is used to multiply the default delays. Setting this value above 1.0 increases the delays,
while a value below 1.0 decreases the delay. Setting this value to 0.0 essentially turns off
measurement delays. This attribute is only used when:
smuX.measure.delay = smuX.DELAY_AUTO.
For analog filter
smuX.measure.analogfilter = 1 (default)
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.
The settling times listed in the specifications found in
of the SMU is approximately 60kHz.
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 8-5
Current source gain-bandwidth
Range
1nA
10nA
100nA
1μA
10μA
100μA
1mA
10mA
100mA
1A
1.5A
3A
8-24
Table 8-5 below.
SMU feedback 60kHz ratio
impedance (DUT / SMU impedance)
1GΩ
120MΩ
40MΩ
1.2MΩ
400kΩ
12kΩ
4kΩ
120Ω
40Ω
1Ω
1Ω
0.3Ω
Return to Section Topics
Series 2600 System SourceMeter® Instruments Reference Manual
-- to turn off measure delay
(default setting is smuX.DELAY_AUTO)
-- set measure delay for all ranges to Y (in seconds)
--To adjust the delays factor:
Appendix A
Table 8-5 below can be used to determine the affect of
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
6
6
5
assume that the gain-bandwidth
Minimum DUT
impedance
2GΩ
60MΩ
20MΩ
600kΩ
200kΩ
6kΩ
2kΩ
60Ω
20Ω
6Ω
6Ω
1.5Ω
2600S-901-01 Rev. C / January 2008