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Question about AC simulation

Gstuarts

I need to run an AC simulation.

I understand that the simulator will first linearize the circuit about the DC operating point, and then compute the response. My problem is that the system I need to simulate has a start-up circuit, and the DC OP is only valid after a few miliseconds. I can obtain the steady state OP from a transient simulation.  How can I tell the simulator to use this OP? 

If I need to run a parameter sweep that will affect the OP, I will need to set this up for every case. Is there a way to do this automatically?

Thank you all in advance!

Guillermo

Parents

  • Hi Guillermo,

    You need to use the "actimes" feature of tran analysis. What you can do is to do a transient analysis to simulate this startup circuit, and then in the transient options form, on the "Output" tab, you can specify the time (or times) at which you want to do the AC analysis. Then having entered these times, you can enter which AC analyses to run at that time (e.g. "ac" or "ac noise").

    Then it will do the small signal linearisation around the condition at that time.

    You can then of course do a parametric sweep around all of this.

    Does that help?

    Kind Regards,

    Andrew.

Reply

  • Hi Guillermo,

    You need to use the "actimes" feature of tran analysis. What you can do is to do a transient analysis to simulate this startup circuit, and then in the transient options form, on the "Output" tab, you can specify the time (or times) at which you want to do the AC analysis. Then having entered these times, you can enter which AC analyses to run at that time (e.g. "ac" or "ac noise").

    Then it will do the small signal linearisation around the condition at that time.

    You can then of course do a parametric sweep around all of this.

    Does that help?

    Kind Regards,

    Andrew.

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