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Design Languages >> Verilog-AMS >> cap model
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Message started by grosser on Aug 23^rd, 2007, 6:39am

Title: cap model
Post by grosser on Aug 23^rd, 2007, 6:39am

hello

i've got one problem in modelling capacitor

i wrote

I(vp,vn) <+ ddt(c*V(vp,vn))

but c=25*limexp(-23.3*V(vin_p,vin_n))

the error message is

line 16: Error: An operand dependent on the output of a dot() operator
(dynamic expression) can not be used in a multiplication operation when
the other operand is dependent on a probe or the simulation time.
Consider using a node to hold the dynamic expression and probe this
node in the multiplication operation.
See also the section of the SpectreHDL reference manual describing
"Time Derivative Operator".

i am beginer and don't understand the proposed solution starting with consider

can you explain me how to fix it?

regards

Title: Re: cap model
Post by Frank Wiedmann on Aug 23^rd, 2007, 6:45am

You can find an example for a varactor model in Listing 1 of http://www.designers-guide.org/Modeling/varactors.pdf. It's probably the multiplication inside the ddt() function that causes your problem.

Title: Re: cap model
Post by grosser on Aug 23^rd, 2007, 7:23am

right, thank you