Under LTSpice, for the VBIC (level=4 or level=9) and MEXTRAM (level=504) Bipolar Transistor Options, as some people pointed me, I dont know how to simulate an e.g. 2N3904 under VBIC or MEXTRAM?
The single reference, suggested by Dietmar Warning (if he is the real) is in sourceforge.net from 2010.
IS the situation still the same?. Or there is a better reference?
I did some BJT modelling previously, from which someone posted a link to the full document on the MEXTRAM model, and also the VBIC model paper may help you.
Here is my condensed advice: don't use the default models from LTspice, write your own .txt file that explicitly defines the parameters that you want.
For example when I was trying to model a germanium BJT I defined a text file called bjtmod.txt, which contained only one line
.model IDEAL_GERM_NPN NPN(IS=1E-6, BF=120, BR=5)
You can see here first the statement is to define a .model, called IDEAL_GERM_NPN, which is an NPN BJT with parameters IS=1E-6, BF=120, BR=5.
To use this in LTspice you must place it in the same folder as the schematic you are working on. Including it to the schematic is done by writing a SPICE statement:
.include "bjtmod.txt"
To set your BJT to use this model make sure that the Value field is set to IDEAL_GERM_NPN.
You can then customize each parameter of the model, including avalanche terms. From the reference you provided:
.model 2n3904L4 NPN(level=4, rcx = 2.65711, rci = 0.0, rbx = 0.634251, rbi = 5.203349, re = 0.0001, is = 1.26532e-10, nf = 1.5, nr = 2.89609, fc = 0.512134, cje = 4.64214e-12, pe = 0.4, me = 0.256227, cjc = 3.015688e-12, cjep = 7.53922e-13, pc = 0.4, mc = 0.238109, cjcp = 0, ps = 0.75, ms = 0.5, ibei = 6.13333850374693e-13, nei = 1.5, iben = 2.30771e-09, nen = 3.31052, ibci = 6.13333850374693e-12, nci = 2.89609, ibcn = 2.30771e-09, ncn = 1.9876, vef = 566.483710419377, ver = 8.69028854282359, ikf = 0.0272221, ikr = 0.272221, tf = 4.19578e-10, xtf = 0.906167, vtf = 8.75418, itf = 0.0105823, tr = 6.82023e-08, td = 0, ea = 1.05, eaie = 1.05, eaic = 1.05, eane = 1.05, eanc = 1.05, xis = 1, xii = 0.9, xin = 0.668948, kfn = 0, afn = 1, avc1 = 0.02, avc2 = 110)
Lastly, don't get fixated on whether it resembles a real BJT. It won't. Some of these parameters vary hugely between devices. Extraction procedures are phenomenally complex, take that from someone who wrote one for only around 12 BJT parameters.
