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I am trying to build a circuit in OrCAD, and I have an inductor with tree terminals. which component should I use for it? L=0.02mHenter image description here

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  • \$\begingroup\$ What are you trying to do, layout a PCB, or simulate it? If you are trying to layout a PCB, you can place any 3-pin symbol and assign the appropriate footprint. If you want to do a spice simulation, you can use 2 inductors with half the value and tap the center. \$\endgroup\$
    – pgvoorhees
    Apr 27 at 23:44
  • \$\begingroup\$ @pgvoorhees Yes, I am trying to simulate the circuit. Ok, I will put 2 inductors next to each other, but what do you mean by (tap the center)? \$\endgroup\$
    – Haspacejar
    Apr 27 at 23:51

2 Answers 2

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In circuit analysis, your inductor with a center tap is considered to be two inductors with mutual coupling.

The way you describe this to a text-based SPICE is with a line that starts with 'K' and specifies a coupling factor between 0 and 1.

Your drawing implies that your coil is air-wound, with all the windings on top of each other. I haven't played with coils like that; I'm assuming a fairly healthy mutual inductance (more than 0.7), but not close to 1, and if you asked me to promise a figure I'd tell you I'd need to go do measurements in the lab.

Unless you're getting something that comes with a data sheet, in order to find your coupling constant you'll need to build the thing and test it. Google for how to do that, and if you don't find anything ask a separate question.

Wires close to wires have mutual capacitance, so your inductor will have a lot of capacitance, and it'll be distributed. While you're testing your inductor to find out its inductance and its mutual inductance, you probably want to find out its self-resonant frequency, or at least verify that its self-resonant frequency is higher than you care about.

PSpice has a graphical way of doing this. I found it by searching on "PSpice" and "mutual inductance". Searching on "PSpice" and "coupled inductors" should help, too.

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If you ignore the fact that on the left are inductors, and on the right is a transformer (the schematic tool doesn't have a "3 terminal inductor"), this is equivalent.

"Center tapped" here means a 3 terminal inductor, where the in between terminal is the terminal-in-common of two equal inductors places in series.

schematic

simulate this circuit – Schematic created using CircuitLab

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