Agilent Technologies Series N6700 User Manual page 34

2 Installation
1. N678xA SMU
connector
2. Guard shield
(can be the
shield of a
coaxial cable)
34
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 power system is sourcing or measuring DC currents under
1 μA. Without a guard, leakage currents in the test circuit could affect
the accuracy of the micro-amp measurements. Guarding is generally
not required when measuring currents 1 μA and greater.
As shown below, cable guards are available at the output 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
+S
+ +
- -
GUARD
+
-
h
G
-S
1
2
Series N6700 User's Guide