NI 655x Termination Summary

NI Digital Waveform Generator/Analyzer

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NI 655x Termination Summary

The following table provides a high-level summary of the termination considerations for your NI 655x. Click a title for more information about that type of termination.

Generation Termination
Source Transmission Line Termination (Load)
Zs = 50 Ω Zo = 50 Ω Zt = Open (Tristate) or Unterminated
Works for all except most demanding applications
Zt = 50–150 Ω
Recommended for better signal integrity.
Acquisition Termination
Termination Transmission Line Source
Zt = 10 kΩ 50 Ω Zs = 50 Ω
This configuration works well for most applications.
Zs < 50 Ω
This configuration is not recommended because of the mismatch on both ends.
The recommended setup is to increase Zs to 50 Ω by adding series resistance at the source.
Zs > 50 Ω
This configuration is not recommended because of the mismatch on both ends.
Note  You must reduce the operating frequency significantly to allow the signal reflections to settle down. You must reduce the frequency proportional to cable length and impedance mismatch.
Zt = 50 Ω Zs = 50 Ω
This configuration is recommended for best signal integrity.
Vi = Vo/2
Source must be able to drive 50 Ω
Zs < 50 Ω
Source-side mismatch degrades signal integrity, but this configuration is still usable in many applications.
Vi = 50/(50 + Zs) * Vo
Zs > 50 Ω
Source-side mismatch degrades signal integrity, but this configuration is still usable in many applications.
Vi = 50/(50 + Zs) * Vo
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