Agilent Technologies Agilent E5250A manual Measurement Cable Length

Setting up Measurement Environment

Measurement Cable Length

Measurement Cable Length

This section describes how to calculate the total guard capacitance when using a Source Monitor Unit (SMU), such as in Agilent 4155/4156 Semiconductor Parameter Analyzer, Agilent 4142B Modular DC Source/Monitor, Agilent E5270 Series of Parametric Measurement Solution, and so on.

When using an SMU, the length of measurement cables is limited by the guard capacitance of the cables. Guard capacitance means the capacitance between the signal line (FORCE or SENSE) and the GUARD line.

Table 4-6 lists the guard capacitance for each element of the E5250A measurement environment.

When using the 4155/4156/4142B/E5270, the maximum limit of the guard capacitance is approximately 900 pF. So, you add the following and total must be less than 900 pF:

•Guard capacitance of cable from SMU to E5250A SMU INPUT.

•Guard capacitance of E5250A and installed plug-in cards.

•Guard capacitance of cable from plug-in card output to connector plate.

•Guard capacitance of cable from connector plate to DUT.

•Other capacitances, such as for probe card.

The following is an example to calculate the guard capacitance of a measurement environment:

Installed Plug-in cards:

Input Cable:

Output Cable:

Cable from Connector Plate to DUT:

Probe Card:

Four E5252A cards (145 pF + 8 pF ⋅ 3)

16494A-003 (75 pF)

16494A-001 (125 pF)

8121-1191, 2 m (130 pF ⋅ 2)

Guard Capacitance approximately 10 pF (example)

In this environment, the total guard capacitance (Cg-total) is as follows.

Cg-total = 145+(8⋅3)+75+125+(130⋅2)+10 pF = 639 pF < 900 pF

Even if you use other instruments, you can use the table for reference about the measurement cable length and capacitance.

Agilent E5250A User’s Guide, Edition 9 4-23