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https://designers-guide.org/forum/YaBB.pl Design Languages >> Verilog-AMS >> frequency dependent capacitor modeling https://designers-guide.org/forum/YaBB.pl?num=1293021428 Message started by rajdeep on Dec 22nd, 2010, 4:37am |
Title: frequency dependent capacitor modeling Post by rajdeep on Dec 22nd, 2010, 4:37am Hi all, I have a requirement where I would like to model a capacitor as a function of frequency. Its like C(s) = C*H(s) where H(s) is a transfer function. To start with, I tried to write the simple frequency model of a capacitor i.e. V = I*(1/sC). I could only think of writing it in the following way: V(p,n) <+ laplace_nd(I(p,n),{1},{0,C}); whre C is constant. [My next step would be to make this C dependent on frequency.] But it doesnt give me expected result, what I usually get if I use a standard capacitor or use I(p,n)<+C*ddt(V(p,n)). I am no longer very fluent with laplace transform, but I would think thats the correct frequency domain model of a capacitor with initial voltage 0. I also wonder is there any other way to express a quantity w.r.t frequency other than laplace transform? By the way, I am using this model for ac analysis only. Thanks, Rajdeep |
Title: Re: frequency dependent capacitor modeling Post by Marq Kole on Feb 2nd, 2011, 6:25am You cannot access frequency directly in Verilog-A. Next to that: AC is a small-signal analysis so in many simulators you will see that non-linear code is only evaluated during DC and the AC behavior is derived from the linearization around the DC solution. The simulator does not need to re-evaluate the model code for that. The AC analysis will only do what you want if you can rewrite your frequency-dependent capacitor as another LTI transfer function. Cheers, Marq |
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