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Old 20th July 2005, 11:44 PM   #1
Jorge is offline Jorge  Brazil
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Default Looking for SPICE models of power BJTs

Hello,

I think there is something weird with OnSemi's models of the MJL3281 and MJL1302.

Does someone have equivalent models from other sources (same voltage/current and FT range).

Thanks,
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Old 20th July 2005, 11:58 PM   #2
tlf9999 is offline tlf9999  United States
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I haven't checked it myself but you may want to look into popular simulation suites (OrCad, PSD, etc.) to see what they use there. As those models in commercial suites tend to be copyrighted, it is hard to share them in public.
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Old 21st July 2005, 12:44 AM   #3
andy_c is offline andy_c  United States
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Default Re: Looking for SPICE models of power BJTs

Quote:
Originally posted by Jorge
I think there is something weird with OnSemi's models of the MJL3281 and MJL1302.
Yes, they are terrible. This thread presents some results showing the simulated ft to be around a factor of 6 low at the nominal bias current. It also shows a PSPICE model which is pretty terrible also. I ended up tweaking the models to get a much better fit to ft vs current. The results are shown later in the thread. Unfortunately, I made the assumption that they couldn't possibly have messed up the DC parameters, but sure enough those are hosed too. This other thread shows some of the problems with the DC parameters. Among these is an RC that's much too high. It causes the internal Vcb to vary with increasing current so much that, combined with the Early effect, it gives a downward tilt to beta vs current.

Unfortunately, I haven't gone back and combined these changes into one model that fixes both the DC and AC parameters. I've been meaning to do it for quite some time now. Maybe this weekend I will bite the bullet and give it a try.
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Old 21st July 2005, 02:27 AM   #4
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Good on you Andy.

You should sell the device manufacturers your improved models of their products! Get paid for it.

Cheers,
Greg
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Old 21st July 2005, 02:57 AM   #5
andy_c is offline andy_c  United States
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Doing this kind of stuff is no fun at all! The data sheets don't give all the info you need to get all the model parameters. Then there's the matter of eyeballing the data sheet to get tons of data values, then manually entering the data into Excel to plot them. What's really needed are text files containing the data for the characteristic curves, ft vs current, etc. It would be way cool if the data for the Gummel plots could be obtained from the vendor as text files.

That's why I've put it off so long.
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Old 21st July 2005, 03:02 AM   #6
Jorge is offline Jorge  Brazil
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Default Hello, Andy

Thanks!

Found your models for the 2SC/2SA ones, for me these are plenty enough.

I was getting weird cross conduction artifacts at 20k - now gone!

And, sice we are at it - some nice models for drivers? (here at DIYA or other site?)

Regards,

Jorge
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Old 21st July 2005, 03:09 AM   #7
andy_c is offline andy_c  United States
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Hi Jorge,

Later in that thread, I did some plots of the MJE15030 and MJE15031 models ft vs. current. This post in that thread shows that the plots agree very well with the data sheet. You might give those a try.
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Old 21st July 2005, 03:25 AM   #8
Jorge is offline Jorge  Brazil
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Tanks again, Andy

i will get them at OnSemi.
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Old 21st July 2005, 10:18 AM   #9
jaycee is offline jaycee  United Kingdom
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Does anyone know if the models for MJL4281/4302 are also flawed?
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Old 21st July 2005, 01:13 PM   #10
MikeB is offline MikeB  Germany
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Yes, they behave similar. At least the last time i downloaded them.
For now, i use the models from andy_c... Thanks Andy !

Mike
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