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Stop Time in Transient Analysis

Hadi Hayati

Hi

I have designed an oscillator which its center frequency is 2GHz and there seems to be a problem with its stop time I guess...

When I choose stop time for example 50ns, the oscillator works well and I can see the output waveforms. And if stop time is greater than 50ns (0.5us for example), then all I have at outputs is a straight line... There is no signal.

Anybody can help me out with this?

 

Regards,

Hadi

 

Parents

  • Hi Hadi,

    The first thing that comes to mind is that the simulator step interval is dependent on the stop time, so as the stop time grows, so does the step interval; this might increase the timestep interval to the point where the oscillator cannot get started.  This might also indicate a possible issue with the simulator tolerances (relative tolerance, absolute tolerance)? You might investigate initial conditions as a way to aid the oscillator starting, or perhaps set the maxstep parameter to about 1/10 of the oscillator period.

    Hopefully this helps.

    Regards,

    Lawrence.

Reply

  • Hi Hadi,

    The first thing that comes to mind is that the simulator step interval is dependent on the stop time, so as the stop time grows, so does the step interval; this might increase the timestep interval to the point where the oscillator cannot get started.  This might also indicate a possible issue with the simulator tolerances (relative tolerance, absolute tolerance)? You might investigate initial conditions as a way to aid the oscillator starting, or perhaps set the maxstep parameter to about 1/10 of the oscillator period.

    Hopefully this helps.

    Regards,

    Lawrence.

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