> Previous contributions to the AboutSpice.com mailing-list

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."
Reply to this contribution | Write to the contributor
Submitted by: jeni on 2005-09-21 10:05:16.
Topic:beta and Rbe of an npn transistor
Body:Hi,
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.

*2N2222A
*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,
Jeni
Reply to this contribution | Write to the contributor

Post a new contribution | Back to the list of topics