How Accurate are Manufacturers' Bipolar Transistor SPICE Models?

Recently I've been working on a few circuits that use discrete bipolar junction transistors (BJT) operating in linear (as opposed to switching) mode. The performance of these circuits depend critically on transistor characteristics, so I've done a lot of LTSpice modeling to understand and improve my designs.

A big problem I've run into is inaccurate manufacturers' SPICE models, which don't match either the datasheet specs or the actual parts. An interesting result has been the growth of amateur or hobbyist model creation, which seems to be centered around the DIY audio community. Many of the resulting models, derived from measurements on purchased parts, are far superior to those from the manufacturer. Caveat emptor, but a lot of the third-party models I've pulled off the web and tested are head and shoulders above the OEM versions.

The example below is the ON Semiconductor (formerly Motorola) D44H11 family, NPN 80V 10A power transistors available in several packages. I am quite deliberately picking on On Semi because, in my experience, many of their BJT models are wildly inaccurate. Other manufacturers certainly aren't perfect, but ON Semi seems to be the worst.

The plots show hFE (current gain) verses IC (collector current), which is a useful parameter to examine for several reasons. hFE is critical in many designs, so an hFE-IC curve is included on most BJT datasheets. It's also very easy to create hFE-IC curves in SPICE, yet hFE's dependence on IC is complex, so the accuracy of a model's hFE-IC curve is a reasonably good indication of its overall quality.

The first image shows the hFE-IC curve from the current On Semiconductor MJF44H11 datasheet. IC is shown from 0.1A to 10A, hFE peaks at around 160, and that, at higher currents, hFE depends on the collector-emitter voltage, VCE. Based on my own measurements, the datasheet is reasonably accurate.

 

 ON Semiconductor MJF44H11 hFE verses IC curve.

 
The next image shows hFE-IC curves extracted in LTSpice from ON Semi's model (blue) and from a third party model (green) created by Harry Dymond (http://www.cordellaudio.com/book/spice_models.shtml). The X-axis (IC) runs from 0.01A to 10A (ignore the "S" units), VCE was 4.3V, and the vertical scale is somewhat different, but it's pretty easy to see that the Dymond model is far closer to the datasheet.

 

 Both models are listed below, and even folks who don't understand SPICE models will see that many of the parameters in the two models are significantly different.

Official ON Semiconductor model:

**************************************
*      Model Generated by MODPEX     *
*Copyright(c) Symmetry Design Systems*
*         All Rights Reserved        *
*    UNPUBLISHED LICENSED SOFTWARE   *
*   Contains Proprietary Information *
*      Which is The Property of      *
*     SYMMETRY OR ITS LICENSORS      *
*    Modeling services provided by   *
* Interface Technologies www.i-t.com *
**************************************
.MODEL mjf44h11 npn
+IS=1.32547e-11 BF=164.27 NF=1.16023 VAF=46.9759
+IKF=4.32946 ISE=2.61723e-12 NE=1.62633 BR=1.80421
+NR=1.16498 VAR=469.765 IKR=0.670133 ISC=2.61723e-12
+NC=3.00051 RB=1.61538 IRB=0.1 RBM=0.1
+RE=0.00864486 RC=0.0432243 XTB=0.1 XTI=1
+EG=1.05 CJE=1.04839e-09 VJE=0.651544 MJE=0.353502
+TF=3.84017e-09 XTF=1.35721 VTF=0.995712 ITF=0.999991
+CJC=3.7959e-10 VJC=0.422311 MJC=0.334082 XCJC=0.803125
+FC=0.533765 CJS=0 VJS=0.75 MJS=0.5
+TR=1.93641e-08 PTF=0 KF=0 AF=1
* Model generated on Feb  7, 2004
* Model format: SPICE3

Third-party Harry Dymond model:

***************************************************************************
*                                                                         *
*  D44H11 model created by Harry Dymond. May be freely distributed with   *
*  the proviso that this header comment is included in its entirety. The  *
*  model is based on datasheet and custom measurements available at:      *
*  https://dl.dropbox.com/s/v95mdjwit237sl5/transistor%20models.zip?dl=1  *
*                                                                         *
*  Please note that fT is not accurately modelled at low voltage. This is *
*  in order to accurately model the transistor at higher voltages.        *
*                                                                         *
*  The model has not been tested at any temperature other than 25 C       *
*                                                                         *
*  If you feel you can improve the model you are of course welcome to do  *
*  so but if you do, please let me know!                                  *
*                                                                         *
*  harry(dot)dymond(at)bristol(dot)ac(dot)uk                              *
*                                                                         *
***************************************************************************
.MODEL D44H11_HD NPN(
+IS=2.14e-10 NF=1.271265 BF=208.89 RB=2 RBM=0.1 IRB=10
+VAF=342 NE=2.7349 ISE=1e-8 IKF=30 NK=0.9687
+BR=4 IKR=1.05 VAR=35
+XTF=1800 TF=1.9e-9 ITF=200 VTF=40
+CJE=1.4e-9 MJE=0.3092662 VJE=0.4723539
+CJC=175.527e-12 MJC=0.383595 VJC=0.479488
+TNOM=25 Vceo=80 Icrating=8 mfg=ON)