Evaluation results: MJL3281A/MJL1302A SPICE Models

[PB2]

Originally posted by andy_c


Hi Pete,

Well, I've got to admit to some embarassment here. When I posted this originally, my thoughts were that they couldn't possibly have messed up something so basic as the DC parameters.

WRONG!!!

But I did discover and fix this later. My web site has new models that fix the DC problems as well. Just click on my web link and there's some pages that describe the whole story. Or you can go directly to the page here

Thanks so much Andy! I find the same thing, every time I think something couldn't possibly be wrong, well think again as they say. I'll check out your site!

Pete B.

[PB2]

I tried the new models - perfect!
Ah, I can sleep better now.
I will read your excellent analysis in detail if I ever have to fix up
some models.

Thanks again,
Pete B.

[teodorom]

Hi Andy,
I'm trying to reproduce your calculations (I want to get better models for the MJL4281 and MJL4302) using your spreadsheet.
My main problem is that, in the spreadsheet you provide, the "Simulated external VBE" and "Simulated IB" are hard coded, i.e. not calculated.
Findind by hand VBE (and the external VBE) as a function of IC is not a trivial task.
I was able to find some result using Mathcad, even if what I get is slightly different from what you state.
The function VBE(IC) depends also on the parameters IS, NF, ISC, VAF, VAR, so I'm trying to understand if even those parameters should be included in the optimization.
Thanks

[teodorom]

since I didn't take into account all the available data.
Sorry about that.
Thanks

[PigletsDad]

There is an Excel spreadsheet for fitting some of the basic transistor parameters to datasheets available here:

http://www.analogservices.com/excel.htm

I have used it to construct models for some of the Sanken power devices; I haven't checked the Ft vs Ic, but the DC fit for Hfe is not bad, although the high current falloff is more abrupt in the real device than the model.

HTH

[lineup]

The on-semi spice models looks not to bad!
Not at this parameter.
Both MJL3281 and MJL1302 Ft vs. Current is reasonable.

[andy_c]

Wow, this is an old thread!

The stuff on my web pages regarding the OnSemi models for these devices is out of date now. I originally did those back in Oct. 2006. Since then, they've come out with new models. I haven't looked at those.

Also, there's several other out of date aspects to my web site. The classic Gummel-Poon model as described in Massobrio and Antognetti does not include the effects of quasi-saturation. M&O describe in their book a quasi-sat model that, at the time of writing of the book, was only implemented in HSPICE. However, now LTspice, PSPICE and probably many others use a quasi-sat model originally described in the article:

G. M. Kull, L. W. Nagel, S. W. Lee, P. Lloyd, E. J. Prendergast, and H. K. Dirks, “A Unified Circuit Model for Bipolar Transistors Including Quasi-Saturation Effects,” IEEE Transactions on Electron Devices, ED-32, 1103-1113 (1985).

I'd love to get a copy of this article if anyone has it.

Secondly, when I did that modeling I was new to Excel, having previously only used it for simple financial calculations. Since then, I bought a book on using Visual Basic for Applications (VBA) with Excel. The technique on my web site has many manual steps. This is because I limited my calculations to what could practically be done using formulas in spreadsheet cells. Using VBA, it's possible to automate that process much more than what is shown on my web pages. I'm currently working on some models for the 2sa1837 and 2sc4793 that use this approach.

Going back through the history of this thread, I had plotted hfe vs. frequency to determine fT. This turns out to be unnecessary in LTspice. Using LTspice, one need only do an operating point analysis. The value of fT is then shown in the SPICE error log. This can be combined with the .STEP directive to get many values of fT for a swept IE.