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Submitted by: Jovelino Cabrera Andrade on 2005-09-30 04:15:40.
Topic:Re: beta and Rbe of an npn transistor
Body:Hi Jeni!
"BF" in the spice sintax is the "beta". Better saying, BF is "spice maximum forward beta" = "HFE in mid-current region". To know what does it mean "mid-current region", you can go to http://www.analogservices.com/excel.htm. Find the item "Appendix -- Theory" ; as you can see, beta is not constant for all Ic's. So, BF is the "maximum beta".
At this page http://newton.ex.ac.uk/teaching/CDHW/Electronics2/userguide/sec3.html#3.4.4 you can see that the spice term RB is " zero bias base resistance". By the way, take a closer look at www.analogservices.com/excel.htm. You will see that sometimes (or almost ever) there isn't a direct correspondence between a parameter of a bjt in the datasheet and the spice parameter. So, the author of this page has developded a Excel sheet that do this conversion. Interesting, no?
Best wishes,
Jovelino Cabrera Andrade
"It is not how much you do, but how much love you put in the doing."
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Submitted by: jeni on 2005-09-21 10:05:16.
Topic:beta and Rbe of an npn transistor
I have a spice model of an npn transistor. Can somebody tell me how much are beta and Rbe? I cannot understand the grammar of spice model.

*Si 500mW 40V 800mA 300MHz pkg:TO-18 3,2,1
.MODEL 2N2222A NPN(IS=8.11E-14 BF=205 VAF=113 IKF=0.5 ISE=1.06E-11
+ NE=2 BR=4 VAR=24 IKR=0.225 RB=1.37 RE=0.343 RC=0.137 CJE=2.95E-11
+ TF=3.97E-10 CJC=1.52E-11 TR=8.5E-8 XTB=1.5 )
* Origin: Mcebjt.lib

Best wishes,
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