[Archive] Problem with electrical circuit

Message by Sylvain Ranvier:
I want to put a capacitor between the gnd (node 0) and one node (let say node 3) and put several bias voltages from this node 3 to a few other nodes, for example:
C 0 3 0.001
V 3 1 0.0
V 3 2 0.0
and that doesn’t work. It complains about forbiden circular or redundant biasing.
However, if I use only one bias from node 3, it works.
For example, the following works:
C 0 3 0.001
V 3 1 0.0
Is there any reason for that or is it a bug?
Thank you,

Message by Christian Imhof:
Hi Sylvain,
as far as I know the circuit editing in SPIS only allows for so called star-shaped networks. This means that everything you introduce must be referenced to one node. In your example it would be best to use node 3 as the reference.
I think if you simply change your first definition into C 3 0 0.001 it should work. However, looking on your second example which worked I am a little bit puzzled because this worked although the rule I mentioned above is violated but you could give it a try. In my models I usually use the ground node as the reference, however, I agree that in your example this is not possible since the biasing is wrt to the node #3. Another possibility would be to “unite” the nodes which are on the same potential (1,2,3 in your example). This works in the simulation although you “loose” some information on the individual nodes in the 1D results. However the different surface potentials on a non-conducting coating will be visible in the 2D plots. Of course this method only works if you want the nodes to be on the same potential.
Here is an example of a circuit file I have used in a simulation which worked:
V 0 1 0.
V 0 2 0.
V 0 3 0.
V 0 4 0.
R 0 5 10000
R 0 6 10000
I hope this helps you.