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2 Installation
NOTE
1. Internal
N678xA SMU
connector
2. Guard shield
(can be the
shield of a
coaxial cable)
36
To minimize inductance, the width (w) of the traces should be at
least as great as the thickness of the dielectric (h). It is better to
make the traces much wider than this minimum requirement in
order to minimize the DC resistance.
w
Low Bandwidth Mode with Remote or Local Sensing
All previously stated wiring requirements still apply in Low
bandwidth mode except for the following.
The 15 cm maximum limit between the sense point and the load
capacitor (see #4) does not apply when using Low bandwidth mode.
Guard Connection
The purpose of a cable guard is to eliminate the effects of leakage
current that can exist in the current path of the external test circuit.
The cable guard can be used when the test fixture requires guarding
and the DC Power Analyzer is sourcing or measuring DC currents
under 1μA. Without a guard, leakage currents in the test circuit could
affect the accuracy of the micro-ampere measurements. Guarding is
generally not required when measuring currents 1μA and greater.
You cannot connect to the front panel binding posts when using the Guard.
You must route ALL wires (guard, load, and sense) through the rear panel
access ports of the N6705B mainframe. Refer to the diagram under "High
Current (50 A) Output Connections" for more information. These access ports
can also be used when extremely precise output measurements are required.
As shown below, cable guards are available at the internal connector
of Agilent Models N678xA SMU. The guard is typically used to drive
the shields of cables and test fixtures. It provides a buffered voltage
that is at the same potential as the + output terminals of the module
connector. The guard current is limited to about 300 μA.
G
G
+S
+ +
- -
GUARD
+
-
h
-S
1
2
Model N6705 User's Guide
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