The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Modeling >> Semiconductor Devices >> Pspice Modeling of BJT
https://designers-guide.org/forum/YaBB.pl?num=1122569567

Message started by vjoshi on Jul 28^th, 2005, 9:52am

Title: Pspice Modeling of BJT
Post by vjoshi on Jul 28^th, 2005, 9:52am

I have to model a real BJT DC characteristics using Pspice BJT Model. I have to change the .Model parameters ISE and NE for drop in BF at low currents Ic .
But I don't know how to calculate the values of ISE and NE. I have read a book on semiconductor device modeling in Pspice and it shows a graph of ln(Ic) , ln(Ib) Vs Vbe . Now if i extrapolate the ln(Ib) graph and calculate the intercept I can find the value of ISE but when I extrapolate the graph I am getting the negative value so i am doing something wrong which i cannot figure out so plz help me .

Title: Pspice Modeling of BJT
Post by viren on Jul 28^th, 2005, 8:47pm

I am trying to fit the DC characteristics of the real BJT which I had attached in my earlier email using a pspice BJT model. I am using the gummel poon model parameters to model the real BJT . I don't know which parameters to change . Since there is drop of gain at low currents I have to figure out how to model it in pspice model of BJt the same loss of gain BF . Since the equation for IB in the book had Ib (nonideal)= C2 Is(0) (e^(q*Vbe/nelkT) -1) I changed the value of C2 and nel to describe the nonideal component of Ib which is dominant at low currents.So let me know if i am going wrong and please refer me to someone who knows about this.