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Our mini-impedance calculator out of the EMC practice for the EMC practice.

For a simple impedance calculation of capacitors, RF chokes, LC low-pass filters, capacitors in parallel and wires.

Gibt es Probleme beim Ausführen dieses Applets?

- Please press the appropriate radio button to choose a component.
- Complete at least two of the three blank fields. If all fields contain values, the impedance will be re-calculated.
- If you like to calculate a frequency or a component value, please delete the appropriate field before.
- You can use a dot or a colon as decimal seperator.
- Choose the decimal unit in the appropriate drop-down box. Decimal units are not allowed with the values.

There is no ideal capacitor and also no ideal RF choke. Anytime^{1)} the characteristics of every electric component are dominated by parasitic effects^{2)}. This is true — no matter if you have a capacitor for 0.1 cent or a high-quality multisegment choke.

So, you always should cast doubts on the results of our impedance calculator. Mooser Consulting explicitely points out the possibility of wrong^{3)} results of this impedance calculator. Mooser Consulting will not be liable for wrong results or any consequences arising out of wrong results.

However, we have tried to consider at least the basic parasitic effects of real components. We are using the actual data of SMD capacitors (X7R)^{4)}. Calculating RF chokes is a little more difficult^{5)}: We are using the average data of various actual RF chokes — different sizes of SMD types and wired types with a ferrite core and a rated current less than 2 A. So, there is a higher uncertainty with the results of RF chokes than with the results of capacitors.

By the way: Our calculator assumes, that your PCB provides ideal connections — without any capacity or inductivity of PCB tracks or wired components. However, in reality there are such effects, eg when connecting a capacitor with 10 mm thin wire there is an additional impedance of a some 10 Ohm at 300 MHz!

The "Round Wires" calculator is designed to estimate the impedance of component leads. This appraisal is based on calculating the inductance only.

To do this there have been made several approximations and disregardings:

- The line has no distributed resistance and no distributed conductance
- The line has no distributed capacitance
- There in no skin effect on the line
- The distance is assumed to be much wider than the diameter
- The distance refers to the centre of a round wire
- The wires are assumed to be solid and round
- The cores of the double line are assumed to have the same diameter

1)In other words: at sufficiently high frequencies.

2) In a first approach, these are resistive losses and the serial inductivity or the parallel capacity.

3) "Wrong" results means: the results could be different from the characteristics of real components.

4) The impedance of Z5U capacitors is nearly the same as of X7R. COG/NPO capacitors have less resistive loss, i.e. the impedance at the resonance frequency is appr. 30% - 50% lower.

5) The reasons for this are (amongst others): type of core (ferrite material), wrapping (one or more layers, multisegment), feeding of the connection wires, shape of core, ...

**Jakob Mooser GmbH**

Amtmannstraße 5a

82544 Egling/Thanning

GERMANY

Tel.:+49(0)8176/922-50 Fax:+49(0)8176/922-52

**Mooser EMC Technik GmbH**

Osterholzallee 140.3

71636 Ludwigsburg

GERMANY

Tel.:+49(0)7141/64826-0

Fax:+49(0)7141/64826-11