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Spice temperature simulation in two different environments

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lapa678

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Hi there!

I started to play with temperature simulation of small analog circuit (including two PNPs, PN2907). Just "by accident" I started to do it in two spice simulators: OrCAD 16.6 and LTSpice IV.

In temperature 27 deg I get the same results. If I change simulated temperature (let say to 50 deg), I get different results :p ...
What's up with that? Is it possible or am I doing something wrong? Which software is more accurate in that sense :>?

Any help will be appreciated!
Cheers!
Tom
 

Are you using the same model library for each component ?
 

Yes, the models of PNP are the same...
 

You must be aware that there are several parameters that define the simulation framework. Are you sure that all these are really configured to the same values ?
 

There are often "dialect" differences between simulators
and sometimes differences in how model params of the
same name, are treated. For example some overlaps are
absolute in some, width-scaled in others and these can
drive differences in S/D leakage for MOS. It wouldn't be
surprising if there were such things in bipolar models.

Simple things like one simulator defaulting to CGS and
the other, MKS units would make things diverge at higher
temps where area dependent leakages get busy.

I'd bet you could drill down to the detailed device level
differences by simulating the devices individually.
 

Thanks for the input!
The models are the same, the pspice options in LTSpice are the same as in Orcad (anyway, Orcad has more options)... are there any others that I could try to tweak/change?

I don't get it :) ... 27deg bot results are the same, 50deg they differ..
Here are screenshots:
LTSpice 27deg LTSpice_27.PNG
OrCAD 27degOrCAD_27.PNG
LTSpice 50degLTSpice_50.PNG
OrCAD 50degOrCAD_50.PNG

Any clue what I might be doing wrong?
Cheers,
Tom

- - - Updated - - -

Solved! Straightforward answer is that if models are the same, then both simulators have to give the same results:)..

The problems was that to do simulations in OrCAD someone was changing TNOM value instead of 'working temperature' and that was screwing up the results. Although I started to do the same thing later on, I noticed that error just now... sorry for the problem and thanks!

Cheers,
Tom
 

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