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# Solving a differential equation using VerilogA Model

Last post Thu, Sep 19 2013 5:56 AM by RFStuff. 0 replies.
 Started by RFStuff 19 Sep 2013 05:56 AM. Topic has 0 replies and 233 views
• #### Thu, Sep 19 2013 5:56 AM

• RFStuff
• Joined on Tue, Feb 5 2013
• Posts 260
• Points 4,565
Solving a differential equation using VerilogA Model
 Dear All,I need to solve a differntial eqaition in my VerilogA marco-modelThe eqaution I want to solve is:-  ddt(V(alpha)) = Vx * V(in)V(in) is the input signal ( as a function of time 't')  to the model.Vx is read from a "table_model" at (t + V(alpha) i.e (  \$(abstime) + V(alpha)  ) To solve this  I did as below:-  // define branchesbranch (alpha) alpha1;branch (alpha) alpha2;I(alpha1) <+ -Vx * V(in); I(alpha2) <+ ddt(V(alpha));    The KCL at alpha forces I(alpha1) + I(alpha2) = 0  and solve the differntial equation.     I went and checked the results.At  \$abstime = t1     Vx * V(in)= x1     V(alpha)= y1At  \$abstime = t2     Vx * V(in)= x2     V(alpha)= y2 I think y2 should be eqaul to          y2= [ x2 * (t2 - t1) ]  + y1.But SPECTRE is showing something different than "y2" .Can anybody please tell where I am going wrong ? Kind Regards,
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 Started by RFStuff at 19 Sep 2013 05:56 AM. Topic has 0 replies.
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