SPICE on transistors

[Alchamist]

I use Cordell's models for the BC550C/560C. I believe they reflect the Fairchild parts. The ONSemi and NXP parts are a bit different.

CordellAudio.com - SPICE Models

The models reflect the "real thing" pretty well as far as I can tell. But BJT modeling is somewhat of an inexact art so far, and you just aren't going to get models that match reality in every aspect. Even if you did you would probably find them inconvenient because they would make simulation very slow.

Hello,

I try to learn creating new transistors and other components models for Tina Ti.What is these codes and where do you get the values from ? I couldn't see this values in datasheets :

NJL3281C - created November 22, 2010 copyright CordellAudio
.MODEL NJL3281C npn
+ IS=5e-12 BF=158 VAF=1000
+ IKF=50 ISE=20e-12 NE=1.5 NF=1.0
+ RB=3.0 RC=0.06
+ CJE=11e-9 MJE=0.35 VJE=0.5 RE=0.0
+ CJC=1.2e-9 MJC=0.5 VJC=0.6 FC=0.1
+ TF=2.7e-9 XTF=7500 VTF=3 ITF=750
+ TR=100e-9 BR=5 VAR=4.3 NR=1.1
+ EG=1.1 XCJC=0.96 XTB=0.12 XTI=1.03
+ NC=4 ISC=0.3e-12
+ IKR=4.4 CJS=0 VJS=0.75 MJS=0.5
+ PTF=0 KF=0 AF=1 Vceo=200
+ Icrating=15 mfg=CA112210

Sorry for my begginer level question.

Thank you
Best Regards

 

[keantoken]

Bf is beta, Is sets Vbe, Vaf sets Early voltage, Ikf sets beta droop at high currents, Ise models beta droop at very low currents, and so on and so on...

The LTspice help file has a list of the parameters and what they do, although there is jargon such as "emission coefficient" which makes it sound more complex than it really is.

Probably the best thing you can do is look up BJT modeling tutorials and PDFs, and skim through them to get the gist of what the parameters do. You will never really understand it until you start doing it, and then you can refer to the PDFs as necessary.

 

[PRR]

> What is these codes and where do you get....

https://www2.eecs.berkeley.edu/Pubs/TechRpts/1975/9602.html

SPICE parameters are quite different from how humans look at a device. SPICE "knows" how a BJT works. These parameters adjust its computations to the specific device-type's size, doping, etc. Nagel's Table A3.4 lists the BJT parameters. (This is as-of 1975, when the BJT model was quite mature and solid, but more parameters may have snuck in since then.)

Most of these parameters are gibberish unless you already have good understanding of how a BJT works, which is not a 1-hour study.

The inconsistency at the top of this thread is perhaps due to vendor technicians measuring slope at a convenient low Vce voltage, too low for the final value observed at high Vce. SPICE "knows" a theory by Early which assumes collector lines are straight and asymptotic to VA; in the low-volt range they deviate. ME may also affect this line.

Nagel's 1973 paper is shorter and goes right to the BJT model.
https://www2.eecs.berkeley.edu/Pubs/TechRpts/1973/ERL-382.pdf

Figure 4 shows the curves questioned at the top of this thread and how VA defines the slope of hFE over Vce.