How can two separate unrelated circuits in orcad capture affect each other??

Discussion in 'The Projects Forum' started by orcaduser, Jun 23, 2014.

  1. orcaduser

    Thread Starter New Member

    Jun 23, 2014
    Hey guys,

    I've been trying to add white noise to a chua circuit(a simple chaotic circuit) using a pwl source.However the results didn't seem quite right.I took the vpwl out of the chua circuit and wire it to a resistor in a separate circuit and the results were surprisingly the same!I even changed the piece wise linear voltage source to a Sin wave source and the results were still the same.So to sum it up,I have a chua circuit which works completely fine alone!,but when I add a voltage source(sin or pwl) to the schematic page it goes wrong.How can two separate circuits affect each other?!
    I add the schematic of my work here. You can see the chua circuit on the left and the vsin source on the right.I am new to orcad so any help would be appreciated.
    Thanks in advance
    Last edited: Jun 23, 2014
  2. mvaseem


    Jan 31, 2014
    As I see, you are adding 10K sine source in the ckt. For a designer they appear two separate ckts. But for a spice simulator, these are just equations to be solved. What might be happening is that, as you add a high freq source, the simulator would be taking different time steps to converge the equations.
    Try using smaller time step value (let's say 1u). Also tighten the tolerances (RELTOL,ABSTOL,VNTOL) to increase accuracy of the simulation.
    orcaduser likes this.
  3. orcaduser

    Thread Starter New Member

    Jun 23, 2014
    Yes that totally makes sense.It's a convergence issue.I'm getting better results now.Thanks.You helped a lot:)