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I have a simple RC circuit as below :

enter image description here

I'm trying to visualize current curve and voltage curve (Vout and I(R1)) vs Vin using LtSpice and I obtain the result below:

enter image description here

It's OK that the Vout is leading Vin. However, I do not understand why the current curve I(R1) is completely out of phase with Vout. Any one have explanation for that ? Thanks for your support.

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    \$\begingroup\$ The voltage across the resistor is in phase with the current through it. \$\endgroup\$ – Chu Aug 6 '20 at 15:10
  • \$\begingroup\$ @Chu: Thanks for your answer. Yes It must be in phase. But I don't understand why I obtain the current (I(R1)) and Vout out of phase. Is there any explanation ? Or How I can fix this ? Thanks. \$\endgroup\$ – geek225 Aug 6 '20 at 15:21
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    \$\begingroup\$ If the current's positive direction is defined, in your simulation, as from ground to Vout that's what you get. \$\endgroup\$ – user128351 Aug 6 '20 at 15:33
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    \$\begingroup\$ Turn the resistor around 180 degrees and you'll get the results you expect. \$\endgroup\$ – The Photon Aug 6 '20 at 15:43
  • \$\begingroup\$ When you use the current probe on LTSpice on that resistor, which direction does the tip of the arrow point? \$\endgroup\$ – Big6 Aug 6 '20 at 16:53
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the same simulationvia LTspice

I simulated the same circuit and current seems fine and I used LTspice XVII. Maybe the issue is your version of LTspice. I think you might try to delete your version and upload the latest again.I hope this fixes your problem.

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    \$\begingroup\$ Now try rotating R1 180 degrees and reconnecting and what do you get? \$\endgroup\$ – Andy aka Aug 6 '20 at 17:17
  • \$\begingroup\$ Yep I got my current out of phase.I didnt know that Ltspice has this issue.The 'plus' terminal of a resistor isn't shown on the schematic so you have no good way of knowing which direction the current actually is. It is annoying :/ \$\endgroup\$ – Damla Celik Aug 7 '20 at 13:24
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    \$\begingroup\$ All 2-pin bidirectional components in all sims have this "issue". Some explicitly show + as in inductors, resistors and capacitors don't. Personally I think they should. \$\endgroup\$ – Andy aka Aug 7 '20 at 13:28
  • \$\begingroup\$ @DamlaCelik It's no issue, it's standard SPICE convention since 40+ years ago: two pin elements have a pre-defined direction of current as a convenience for the matrix solver. Elements with more than two pins consider the current as going into the pin. And, as a general rule, don't rush to blame the tool ("Maybe the issue is your version of LTspice", or whatever other simulator); instead, try to first learn what that tool does and how. \$\endgroup\$ – a concerned citizen Aug 7 '20 at 13:47
  • \$\begingroup\$ @Andyaka: I think you for your answer. It resolves my issue. I have just rotate the R1 like you tell me and all it's OK. \$\endgroup\$ – geek225 Aug 7 '20 at 13:52

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