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I was assembling a PCB today which had a circuit to connect the main module to an active GNSS antenna. I noticed that the inductor, a 47nH datasheet, had polarity markings on it, but I was unsure the proper orientation.

circuit

Could someone explain how this inductor could be polar and which orientation is correct in respect to the circuit diagram? I am not an expert in circuits by any means but I thought that an inductor was just a wound coil.

Feynman137
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    [Related.](https://electronics.stackexchange.com/questions/359207/why-does-this-two-terminal-inductor-have-a-polarity) – JRE Jun 28 '21 at 06:19
  • @JRE thanks for sharing this link. From what I gathered the inductance can vary with placement and one should keep placement on all boards the same when possible. Also there are a few placements that give inductance values closer to the spec than others? – Feynman137 Jun 28 '21 at 12:56
  • As far as I can tell, it depends on what other components and materials are near the inductor. The idea is to be consistent rather than achieving some specific inductance. – JRE Jun 28 '21 at 12:59

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"Polarity" is a misnomer here. An inductor is just a coil of wire, after all. But the two ends could do different things.

If it makes any difference, it would have to do with the internal construction of the inductor -- either it's shielded, and there's a break in the shield at one end or another, or it's multiple-layer and the polarity mark indicates the outer (or inner)layer, etc. Differences such as these may have bearing on how you locate other components, or whether you put a ground plane underneath the thing.

I would get onto the MuRata website and dig. See if there's a page on the website or in the catalog of that series of inductor, and see if it says what the polarity mark means.

TimWescott
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