Sweep errors

By "sweeping tool" do you mean parametric sweep in the Analog Design Environment (Tools->Parametric Analysis). If you get a different answer (at least if it's a significantly different answer), it usually means that your circuit has more than one stable operating point, and it depends on where it starts from as to which operating point you get. If you have multiple operating points, simulators cannot guarantee to give you the one you want - they are each equally valid.

You can use the rebuild_matrix option on Simulation->Options->Analog (Algorithm Tab) (set to yes) to force it to rebuild the matrix at each point in a sweep, which can lead to more consistency at the expense of performance. Bear in mind however that these results are not any more correct than the others though...

If you're talking about a PSS sweep (especially if there is a sweep on the PSS form), then in general we don't restart from scratch each time (this tends to help with convergence). There's an option on the main PSS form (it depends on the version of IC you're using as to precisely where this is) which is called something like New Initial Value For Each Point (restart). You can set this to "yes" too (you may need the rebuild_matrix too, if it's a DC operating point related issue).

Turning these on all the time is not a good idea though, because it will slow down  your simulations unnecessarily.

Of course, there's always the possibility that this is a genuine bug, although in practice I don't recall seeing any real issues like this for some considerable time. You can always go to customer support so that we can look at your testcase together.

Regards,

Andrew.

Hi Andrew

Thank you very much for your detailed response.

To give an example, I have a very simple amplifier and I want to sweep the input power in order to find maximum PAE and to see how gain evolves as input power increases. As you mentioned I use Tools->Parametric Sweep. The results are not consistence with when I do them point by point myself.

The other circuit was an oscillator where I wanted to sweep the load resistance to find the maximum output power and again sweeping and doing point by point gave me different results.

I will try to apply what you mentioned above to see if it helps in my case or not.

Thank you very much,

Hamid