Comparison between .model libraries . Very different data found. Why?

Thread Starter

DaniKowa

Joined Jul 1, 2021
46
Hi, the other day I was talking to a friend about the reliability of libraries .model in simulators . It claims that it can happen and not infrequently, that the spice files are incorrect and as a result the simulation may be incorrect!. He gave me two sample files of a transistor for which he had problems saying that one of these models gave him busted results in the simulation. He talks about completely different numerical values. Since it also happened to me to have unexpected results and I did not understand why, I place the two of that .model for comparison. Thanks.

1) .MODEL BC549B NPN IS=4.679E-14 ISE=2.642f ISC=2.337E-14 XTI=3 BF=458.7 BR=11.57 IKF=0.1371 IKR=0.1144 XTB=1.5 VAF=52.64 VAR=364.5 VJE=0.5591 VJC=0.1994 RE=0.2598 RC=1 RB=1 RBM=1 IRB=1E-06 CJE=1.229E-11 CJC=4.42p XCJC=0.6193 FC=0.7936 NF=1.01 NR=1.019 NE=1.581 NC=1.164 MJE=0.3385 MJC=0.2782 TF=4.689E-10 TR=1m2 ITF=0.8842 VTF=2.828 XTF=160 EG=1.11 VCEO=30 ICRATING=100m MFG=PHILIPS
2) .MODEL BC549B NPN IS =1.8E-14 ISE=5.0E-14 NF =.9955 NE =1.46 BF =400 BR =35.5 IKF=.14 IKR=.03 ISC=1.72E-13 NC =1.27 NR =1.005 RB =.56 RE =.6 RC =.25 VAF=80 VAR=12.5 CJE=13E-12 TF =.64E-9 CJC=4E-12 TR =50.72E-9 VJC=.54 MJC=.33
 

Thread Starter

DaniKowa

Joined Jul 1, 2021
46
I did a check with LTSpice and both .model seem to work and give similar results. So they seem to work despite structurally different. I did not ask Which program he had problems, but I would think that it is not LtSpice I put these parameters directly in the library, but I also attached the model files in txt format if necessary.
 

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ericgibbs

Joined Jan 29, 2010
14,130
hi D,
Downloaded your zip, will give a run.

Note: that some models for the same device have more parameters defined, so the listing looks bigger/different, depending on which manufacturers datasheet that has been used for the model.

E
 

Papabravo

Joined Feb 24, 2006
17,240
Transistors themselves do not have a "standard" behavior and neither do their models. The models are created at different times by different groups for different purposes. There is no standards body that pronounces this or that model "compliant" or "verified". I have 12 different models for the TIP31C, each of which produces different characteristics. I have found that the only way to compare "models" is to put the parameters into a spreadsheet in standard order with standard numerical formatting so they can be compared side by side. Comparing the text descriptions is almost useless they are identical because the order of the parameters can be scrambled.

I'd be interested in hearing from anyone with a practical idea on how to deal with this problem.
 

Thread Starter

DaniKowa

Joined Jul 1, 2021
46
@ericgibbs
Thanks for the answers. The BF value in the .model what does it correspond to? Is it possible to find a list with the meaning of these acronyms?

@Papabravo
I think so, too. I have seen that these parameters can also vary from the production batches as well as the manufacturer. But if there are more substantial differences, there is probably a problem in the model. But not in this case. One idea would be to use the average value that is produced by comparing all values of that type.
 

Papabravo

Joined Feb 24, 2006
17,240
BF is the "Beta Factor". It is used to compute the Beta for various combinations of voltage and current.

A more detailed description of the spice parameters can be found in:
D:\USD\OUP\print\cem.DVI

or by googleing "DeviceParametersinSPICE"
 
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