8-24
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2600S-901-01 Rev. C / January 2008
Section 8: Source-Measure Concepts
Series 2600 System SourceMeter® Instruments Reference Manual
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
-- to turn off measure delay
(default setting is smuX.DELAY_AUTO)
smuX.measure.delay = Y
-- set measure delay for all ranges to Y (in seconds)
smuX.measure.delayfactor = 1.0
--To adjust the delays factor:
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
assume that the gain-bandwidth
of the SMU is approximately 60kHz.
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
below.
Table 8-5
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