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Why PSS gives OScillation to Free Running VCO without any initial condition but NOT transient ?

RFStuff

Dear All,

I simulated a LC oscillator in PSS in Oscillator mode even if I have not given any initial condition (Convergence Aid).

While if I run the same oscillator in TRAN  without any initial condition it never oscillates.

Could anybody please tell me what is the reason behind this ?

Kind Regards,

Parents
  • Dear RfStuff,

    If you are not doing so already, might I suggest you set the value of maxstep in your pss and transient simulations to a value of say, 1/20 or less, then the expected period of the oscillator. Often an oscillator will not start in an analog simulation if the default timestep (which depends on the value of errpreset you have chosen and the total simulation time period) is not sufficiently small. This may avoid the need to use an initial condition file.

    Shawn
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  • Dear RfStuff,

    If you are not doing so already, might I suggest you set the value of maxstep in your pss and transient simulations to a value of say, 1/20 or less, then the expected period of the oscillator. Often an oscillator will not start in an analog simulation if the default timestep (which depends on the value of errpreset you have chosen and the total simulation time period) is not sufficiently small. This may avoid the need to use an initial condition file.

    Shawn
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