I dont think you can build a pure sine wave current source with just passive components, but with active components you could build something that resembles this very closely. The wave 1-cos(t*w) times any constant is a wave that is always above zero, not a sine wave. So we end up with a DC offset across the cap with a sine source.
This results in a response not of a pure sine wave, but as: It could also be that it does not like the starting condition of a zero voltage across the cap when there is zero current through it and it's driven by a sine source. They dont want any "open" circuits for DC current because then even the tiniest DC current would eventually cause an infinite voltage which would then mess up the calculations for the entire matrix (BTW we looked at the effects of a small offset DC current through a capacitor in another thread).Īs we were saying, it could be just because the program is written to not allow any node to exist without a DC path to ground so that it wont ever be able to develop an infinite voltage, but you could try connecting a large resistor across the cap to find out. For example, if you 'could' have a floating DC source of 10 volts for example one terminal would read "-5v" and the other "+5v". You'll note that in simulators things are a little different than in real life because certain concessions have to be made. The fix is a 10 megohm resistor connected from one side of the source to ground.
#Qucs noise voltage source full
In some simulators this happens with an AC voltage source driving a full wave bridge rectifier, where the bridge then drives a capacitor with one end of the cap connected to ground (so the source seems to be floating). What always solves these problems however is to connect a very large value resistor (like 10 megohms) from the node to ground or from the node to some DC source voltage.
#Qucs noise voltage source series
You could also try the two caps in series test and use a voltage source or something but dont connect anything to the junction of the two caps.
To find out more, you could try using a DC current source and see if that changes anything. Or, it could be that the source is an AC source so it thinks the upper node is open for DC current. In your case it could be happening because the upper node is connected to only a capacitor and a source that might be considered an infinite resistance for DC current, so that may trigger the complaint. It is usually the DC status of a node that triggers an error like this so if you had say just two capacitors connected in series with the two open ends connected to DC sources it might complain that the common node was "open circuit" or some other complaint like "node n has no DC path to ground".
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