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Modeling >> Semiconductor Devices >> How to fit the knee voltage of Vbe of BJT ?
https://designers-guide.org/forum/YaBB.pl?num=1123278045

Message started by vjoshi on Aug 5^th, 2005, 2:40pm

Title: How to fit the knee voltage of Vbe of BJT ?
Post by vjoshi on Aug 5^th, 2005, 2:40pm

I am now able to model and get the Ib vs Vbe curve but the knee voltage of Vbe of the measured BJT model is 2.7 V and I am getting .8 V for my pspice model. What parameters should I change to get the knee voltage of Vbe to 2.7 V ?

Title: How to fit the knee voltage of Vbe of BJT ?
Post by vjoshi on Aug 11^th, 2005, 6:19am

I am able to model the Ib vs Vbe curve of the real BJT with the pspice model of BJT. I changed the values of ISE and ISC. I wanted to know if I could reduce the slope of the curve between 0 V and 2.7 V to zero so that it matches perfectly with the real BJT Ib vs Vbe curve.
Thanks

Title: Re: How to fit the knee voltage of Vbe of BJT ?
Post by Geoffrey_Coram on Aug 18^th, 2005, 10:07am

You can try changing the emission coefficients or perhaps the series resistances (rb, re). 2.7V is a pretty high voltage for the knee. Most diodes have a knee of 0.5 to 0.8 V. Are you sure your measurements are right?