Electronic Circuits and Projects Forum

hi,

Open the following file, using a text editor and paste the model details listed below, into the
C:\Program Files\LTC\LTspiceIV\lib\cmp\standard.bjt

Paste it at the top of the other transistor models in that file, Save the standard.bjt file.

Run LTspice and using F2 , select a 'npn' transistor an place the symbol on your circuit.

Right click on the transistor symbol and then 'pick new transistor button', your NEW transistor 2N3393 should appear, select it.

I have a asc file and image to help you test , AFTER you have added the new model.



.MODEL 2N3393 NPN(IS=12.03E-15 ISE=8.195E-12 ISC=0 XTI=3 BF=154.1 BR=4.379 IKF=0.1072 IKR=0 XTB=1.5 VAF=37.37 VAR=12.5 VJE=0.65 VJC=0.65 RE=0.1 RC=1 RB=10 CJE=8.307E-12 CJC=5.777E-12 XCJC=0.75 FC=0.5 NF=1 NR=1 NE=1.971 NC=2 MJE=0.384 MJC=0.3199 TF=385.4E-12 TR=783.8E-12 ITF=0.17 VTF=3 XTF=8 EG=1.11 KF=1E-9 AF=1 VCEO=25 ICRATING=500M MFG=NSC)

Originally Posted by aussiebloke

G'day. Thanks for helping but that wasn't quite the answer I was after nor that was the question I was actually asking. That particular transistor I am aware is already in the models list in standard.bjt and I actually cut and pasted the given code for that 2N3393 transistor from standard.bjt as an example showing what kind of mumbo jumbo coded parameters LTspice uses to specify transistor values instead of having a user friendly parameter settings for us to add new transistors such the data on transistors listed on alltransistors.com .

What I want to know is when I want to add new transistors to the standard.bjt, how do I convert the transistor specifications like max collector-base voltage, max collector current etc. to the mumbo jumbo code LTspice uses such as ISE= ISC= BF= BR= etc.? I basically want to enter all those listed old germanium transistors into standard.bjt with the appropriate codes that represent those transistors' specifications so I can accurately reconstruct sections of the camera's circuits where the transistors are in LTspice, run the appropriate signals through them and look at the output signal, then after that replace the germanium with a silicon and the appropriate resistors to make the silicon do the job similarly to the germanium and test the output signal to see if it's the same so I know if it will work or not.

That "mumbo jumbo code" consists of standard Spice parameters used in all Spice type programs, which allows accurate simulation of the transistor operation under a wide variety of operating conditions. The parameters in a data sheet tell only enough about the transistor for the designer to use it in a circuit but not enough to accurately simulate its operation. The data sheet parameters can be converted into the spice parameters with limited accuracy. See this for a program (SpiceMod, not free) that does just that.

So otherwise you could try to find some Spice parameters for similar germanium transistors and put them into LTSpice. The simulation won't be exact, but it should be close enough to tell you how the circuit operates. And there likely isn't that much difference between the circuit operation with germanium and with silicon, other then possibly having to adjust the base bias resistors to allow for the different Vbe.

SPICE parameters seem to bear no resemblance to their datasheet equivalent so you have my sympathy. Trust the mumbo jumbo and assume it is close to the datasheet performance of the part and the simulation should be accurate. Have a look at the link below for more information on importing 3rd party spice models. personally I do not import them into the standard library. If I ever have to reinstall LTSpice, I believe the standard library (hence all your models) gets deleted. I keep all the models in a separate directory

Originally Posted by simonbramble

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personally I do not import them into the standard library. If I ever have to reinstall LTSpice, I believe the standard library (hence all your models) gets deleted. I keep all the models in a separate directory

What I do, if I have to reinstall a program is to save all the libraries under a different name before the install. Then you can remove the new libraries and change the saved file names back to the original after the installation is complete and nothing is lost.