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Impedance Matching Termination Calculator

Work out impedance matching termination instantly with clear inputs, formula shown and shareable results.

About Impedance Matching Termination Calculator

Series termination adds Z0 minus the driver impedance at the source and dissipates no static power, but only works point to point. Parallel termination at the receiver matches the line for multi-drop and better signal fidelity, at the cost of continuous DC current.

Formula

Termination

series R = Z0 - Zdriver; parallel R = Z0; Thevenin uses two resistors of 2 Z0; reflection = (ZL - Z0)/(ZL + Z0)

Worked example

With the default values below, Impedance Matching Termination Calculator returns Termination resistor of 25.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Trace impedance
50 Ω
Driver output impedance
25 Ω
Receiver impedance
10,000 Ω
Termination schemeone of Series (source) termination, Parallel (end) termination, Thevenin split termination, AC / RC termination
Series (source) termination

Results

Termination resistor
25.00 Ω
Reflection coefficient
0.00000
Reflection
0.000% %
Static power penalty at 1 V
0.00 mW

Step by step

  1. 1Values used
  2. 2Termination
  3. 3Termination resistor= 25.00 Ω
  4. 4Reflection coefficient= 0.00000
  5. 5Reflection= 0.000 %
  6. 6Static power penalty at 1 V= 0.00 mW

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Which scheme should I use?

Series for point-to-point CMOS signalling where power matters. Parallel or Thevenin for multi-drop buses and high-speed links where reflections must be killed at the far end.

Why does AC termination save power?

A series capacitor blocks DC, so the resistor only damps transitions. The trade is a frequency-dependent match and a settling time constant.

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