Pspice : Model a capacitor using 'charge Source'

Hi,

The question is related to Pspice modeling.

I want to model a capacitor using the equation Q = C*V.

The reason behind this implementation is,
1. I can access the voltage across this charge source.
2. I can model a capacitance which has the dependency on the voltage across it.

In pspice reference manual, there is way to model a 'charge source'.

Gbc p n Q= {C * V(p,n)} ==> models the charge source.

But, I am not able to simulate this model. The tool understands this statement but throws the following error.

"Less than two two connections at node p and n"
"nodel p and n are floating"

I have attached the detailed screenshots of the error message and the model.

Please help.

Regards,
Jebas.

for the error message , try to include a verylarge value resistance like 1 giga ohm between plus and minus nodes.

Hi,

Thanks for your suggestion.

But, it has not solved the problem. Still the same error.


Thanks.

jebaspaul said:

Hi,

"Less than two two connections at node p and n"
"nodel p and n are floating"

Click to expand...

did you get the same two errors?

or only one?

make a gnd at n node and please report the outcome.

Are you sure that your subcircuit nodes are correctly connected in the component symbol? Die you review the generated netlist?

Hi,

Finally I am able to model it using LAPLACE equation.

Glaplace p n LAPLACE {V(p,n)} {s*C} ==> This implements a voltage controlled current source with a transfer function of I(s) = V(s) * s * C.

I find this implementation is useful,
1.When anybody wants to convert a Hspice capacitance model to pspice capacitance model.
2.If anybody want to implement a capacitor with higher order voltage dependency. E:g : Ceq = C*(1+vc1*v(p,n) + vc2*v^2(p,n) + ...)

The equation mentioned in the second point can be implemented as follows,

G1 p n LAPLACE {V(p,n)} {s*C}
G2 p n LAPLACE {V(p,n)} {s*C*vc1}
G3 p n LAPLACE {V(p,n)*V(p,n)} {s*C*vc2)

This implements a three capacitors which are placed in parallel.

Note: This is another way of implementing a voltage depended capacitance in Pspice. So,my query on implementing capacitance using 'charge source' model (voltage controlled charge source) is still open.

@FvM : Yes, I have checked the netlist. that is fine. The sub-circuit nodes are correctly connected in the model symbol. You given explanation for this error in another thread - will it be applicable here also. (https://www.edaboard.com/threads/314083/


@srizbf : Still the same error messages.


Regards,
Jebas.

can you connect the 1gigohm in the subcircuit defintion of cap_t and run the simulation?

and also make a gnd in your main circuit.