Indeed, a resistor in parallel with the current source will solve the problem. What I don't understand is how a node can be 'floating'. Steve gave the answer, perhaps I can put it this way: the node is 'floating' because the software can not decide its voltage, correct?When you got the error, was there a help button?
Typically, you need to have the equivalent of an internal resistance shunting the capacitor terminals, or that could be considered an irregular circuit. Place a 1 Meg resistor in parallel with the current generator and see if that clears the error.
According to twiki ...LTspice does not report an error for a current source driving a capacitor so not sure why PSpice does(?).
I realize the following is not in English ... but you might glean some info on correcting the problem your having.As a convergence aid, floating nodes in LTspice include a hidden default shunt resistance to ground.
Floating nodes are typically created when only connected to capacitors and/or current sources.
I must have missed this thread earlier...
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".
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. Or, it could be that the source is an AC source so it thinks the upper node is open for DC current.
To find out more, you could try using a DC current source and see if that changes anything. 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.
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.
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). The fix is a 10 megohm resistor connected from one side of the source to ground.
You'll note that in simulators things are a little different than in real life because certain concessions have to be made. For example, if you 'could' have a floating DC source of 10 volts for example one terminal would read "-5v" and the other "+5v".
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).
Thank you very much MikeMl. You gave simple, clear and direct answers to my questions.In the current-source driving a capacitor circuit, in the real world, it isimpossible to build a current source that doesn't have some resistance shunting it, or that doesn't have a dc offset. It is impossible to build a capacitor that doesn't have some internal DC leakage.
In the current-source driving a capacitor circuit in parallel with a voltage source, it your lack of understanding of KVL is causing your confusion. The impedance of an ideal voltage source is zero, so the voltage across the capacitor will be 1mV, regardless of the what the current source is doing.
And thank you very much MrAl, especially for your patience with my silly questions. : )A simulation is only as good as how the circuit you enter models reality. Reality dictates that capacitor and/or current source be shunted with a high, but finite resistance. Put it in explicitly with PSpice, or let LtSpice put it in for you...