I-6
Applications Guide
Model 6485 Picoammeter Instruction Manual
Figure I-3
Simplified model of a feedback picoammeter
Source capacitance
DUT source capacitance will also affect the noise performance of the Model 6485 picoam-
meter. In general, as source capacitance increases, the noise also increases. To see how
changes in source capacitance can affect noise gain, again refer to the simplified picoam-
meter model in
. The elements of interest for this discussion are the source
capacitance, C
S
and the feedback capacitance C
F
. Taking into account the capacitive reac-
tance of these two elements, the previous noise gain formula must be modified as follows:
Table I-1
Minimum recommended source resistance values
Range
Minimum Recommended Source Resistance
2nA, 20nA
1 M
Ω
to 1 G
Ω
200nA, 2µA
10 k
Ω
to 10 M
Ω
20µA, 200µA
100
Ω
to 100 k
Ω
2mA, 20mA
10
Ω
to 1k
Ω
R
F
C
F
-
+
V
noise
R
S
C
S
V
S
V
O
Z
F
Z
S
6485
Picoammeter
Current
Source
Output V
NOISE
Input V
NOISE
1
Z
F
/Z
S
+
(
)
=
Содержание 6485
Страница 1: ...Model 6485Picoammeter Instruction Manual A G R E A T E R M E A S U R E O F C O N F I D E N C E ...
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Страница 44: ...1 20 Getting Started Model 6485 Picoammeter Instruction Manual ...
Страница 66: ...3 6 Measurements Model 6485 Picoammeter Instruction Manual ...
Страница 138: ...9 20 Remote Operation Model 6485 Picoammeter Instruction Manual ...
Страница 159: ...11 CommonCommands ...
Страница 164: ...11 6 Common Commands Model 6485 Picoammeter Instruction Manual ...
Страница 165: ...12 SCPISignalOriented MeasurementCommands ...
Страница 190: ...14 12 SCPI Reference Tables Model 6485 Picoammeter Instruction Manual ...
Страница 214: ...16 14 Calibration Model 6485 Instruction Manual ...
Страница 219: ...A Specifications ...
Страница 221: ...B StatusandErrorMessages ...
Страница 227: ...C GeneralMeasurement Considerations ...
Страница 233: ...D DDCEmulationCommands ...
Страница 247: ...E ExamplePrograms ...
Страница 250: ...E 4 Example Programs Model 6485 Picoammeter Instruction Manual ...
Страница 251: ...F IEEE 488BusOverview ...
Страница 266: ...F 16 IEEE 488 Bus Overview Model 6485 Picoammeter Instruction Manual ...
Страница 267: ...G IEEE 488andSCPI ConformanceInformation ...
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