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Is it Me, Kirchoff or LTSpice that's not working here?

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righteous

righteous

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Engineers and other good people,

I ran into what seems to be a malfunction of something, Kirchhoff's Law states "The algebraic sum of currents in a network of conductors meeting at a point is zero." But here it only seems to be true for the positive period of a sine, can anyone explain it? look here:

Screenshot from 2017-12-17 11-58-09.png

Regards.
 

Hi,

Yes, diode current has wrong direction.

Klaus
 

Hi,

I personally don't like to relate the current direction here on the diode orientation.

According Kirchhoff one need the same direction to/from the node for all currents
--> Either all current vectors need to point to the node
...or away from the node.

Klaus
 

KlausST said:
I personally don't like to relate the current direction here on the diode orientation.
Click to expand...
It is a usemodel of measuring device(or instance) current in SPICE.

On the other hand, we measure terminal current in Cadence Spectre.

KlausST said:
According Kirchhoff one need the same direction to/from the node for all currents
--> Either all current vectors need to point to the node
...or away from the node.
Click to expand...
Terminology of "node" is used for Voltage in SPICE Type Simulator.

In this case, there are three terminals connected to one node.
 
Last edited:

KlausST said:
Hi,

I personally don't like to relate the current direction here on the diode orientation.

According Kirchhoff one need the same direction to/from the node for all currents
--> Either all current vectors need to point to the node
...or away from the node.

Klaus
Click to expand...

ahh ok, in LTSpice the diode current vector is to the node, the other two are from the node. So LTSpice is not Kirchoff compatible (in lack of a better word)?
 

So LTSpice is not Kirchoff compatible (in lack of a better word)?
Click to expand...
It's your job to arrange the current measurements in accordance with the circuit function. Each two terminal component has a fixed current measurement polarity assigned. If it doesn't point the right way, use a minus sign.

ltpice.png
 

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