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Modeling Vout = Vin *{ 1-exp[-(t/alpha)^beta] } (Read 864 times)

jszair

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Modeling Vout = Vin *{ 1-exp[-(t/alpha)^beta] }
Jul 10^th, 2016, 4:02pm

Hello,

I want to model a block that produces the following behavior

Vout = Vin *{ 1-exp[-(t/alpha)^beta] }

Since it has exp[-(t/alpha)^beta], I can't simply use an RC like behavior model.

Modeling it with an varying RC as a function of Vin of previous timestep is also tricky, any error will be blown up because of its exponential behavior.

Any suggestions?

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Geoffrey_Coram

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Posts: 1998
Massachusetts, USA

Re: Modeling Vout = Vin *{ 1-exp[-(t/alpha)^beta] }
Reply #1 - Jul 25^th, 2016, 5:45am

You can write that equation exactly in Verilog-A, if your simulator supports it. There are also some simulators that allow you to specify expressions for dependent sources, though I'm not sure if you can use time in those expressions.

Code:

`include "disciplines.vams"

module myfilter(in, out);
  inout in, out;
  electrical in, out;
  parameter real alpha = 1;
  parameter real beta = 1;

  analog begin
    V(out) <+ V(in) * (1 - exp(-pow($abstime/alpha, beta)))
  end
endmodule

If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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AMS_ei Community Member Offline Posts: 67	*Re: Modeling Vout = Vin { 1-exp[-(t/alpha)^beta] } Reply #2 -** Jul 30^th, 2016, 5:28am There will be a ";" at the end otherwise, it will shout with compilation error. Here is the correct ones: analog begin V(out) <+ V(in) * (1 - exp(-pow($abstime/alpha, beta))); end
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