Adding a Model of the 741 Op Amp to LTSPICE
Step 1) Create a new folder in the LTSPICE subcircuit directory. It is probably
something like C:\Program Files\LTC\LTspiceIV\lib\sub on your computer. For
simplicity, I called it BEE215. So you should end up with something like:
C:\Program Files\LTC\LTspiceIV\lib\sub\BEE215
Step 2) Create a new folder in the LTSPICE symbol directory. It is probably
something like C:\Program Files\LTC\LTspiceIV\lib\sym on your computer. Also call
this folder BEE215. So you should end up with something like:
C:\Program Files\LTC\LTspiceIV\lib\sym\BEE215
Step 3) Find a spice model for the 741 op amp (usually with a .MOD file extension).
A first guess at a good source would be the manufacturers website, and sure enough,
National Semiconductor has a model file available for the LM741. This particular
model can be found here:
http://www.national.com/models/spice/LM/LM741.MOD
Download this small file and copy it to the sub\BEE215 directory you created in step 1.
So this folder should now contain a file called LM741.MOD.
C:\Program Files\LTC\LTspiceIV\lib\sub\BEE215\LM741.MOD
Step 4) Now for a slightly tricky part. Open up the LM741.MOD file you downloaded
with a text editor such as Wordpad. Find a line in the file that should read: .SUBCKT
LM741/NS 1 2 99 50 28
Edit the text LM741/NS to read LM741 (remove the /NS)
The line should now read: .SUBCKT LM741 1 2 99 50 28
Save the file into the same directory as LM741.lib. You can delete the LM741.MOD file
now if you want to.
LTSPICE subcircuit files need the .lib extension.
Step 5) Now we need a symbol for the spice model of the 741 op amp we
downloaded. You can create your own symbols from scratch, but it is easier in this
case to just copy an existing symbol of a similar component and modify it. The symbol
for the generic part opamp2 in the LTSPICE symbol directory will do nicely. On your
computer it is probably located at:
