LTSpice Symbol Editing Question

After about 2 months since downloading LTSpice, I've come to recognize it as an easy to use and valid time saving tool, limited only by its libraries of components. I want to lessen that limitation by further building the libraries.

Question: Can one use existing external topologies of devices resident in the LT libraries or other devices resident as downloaded as exemplars for the .sym file, copied to elsewhere and renamed as another device of the exact external topology, or is one required/limited to use the generic configurations offered? Reason for question is to eliminate the need for .inc Spice directive.

Additional questions may follow if my gray matter solidifies permanently to granite.

Thank You in Advance,
Merv

Yes, I "borrow" the symbols from some of the components supported by LTC, and reuse them with text-based Spice models from other vendors.

btw- have you seen this? Lots of good models in the download.

Mike,

Thank you for the link and for the response. Unfortunately, I have not come across the method of not requiring the include directive within a symbol able to be edited. How do you edit a symbol not requiring the include directive? I'm an impatient old fart suffering from CRS, and get frustrated when I forget 1-5 includes.

Cheers,
Merv

Is the library that contains the .subckt in the same directory as where the .asc circuit file is, or is the library in C:\Program Files\LTC\lib\sub\?

put the symbol in /sym, and the subcircuit in /sub LTSpice's internal pointers go there. the symbol will show up in the lcomponent list (IIRC, you have to restart LTSpice).

you will have to use a .include statement for imported models, except for transistor and diode models. you can copy the appropriate .model text to the standard.dio, standard.bjt, or standard.mos files (found in /cmp), and it will be accessible through the drop down lists.

Mike and UncleJed,

Thanks for responding.

Yes, I've made sure each .sub file is in the .sub directory as a .sub file. The few symbol files I have are in the proper sym directory as .asy files. It's the .sub files that have no complimentary .asy files that I'm trying to use a universal "pseudo" file of the same external topology, op amps for now, that I'm trying to find a work around to keep from having to remember applying the .inc Spice directive. Perhaps I'll just have to delve into the possibility of building my own generic editable asy file and use it for those devices without symbol files, if that is possible in LTS. Otherwise, I'll just have to REMEMBER the .inc directive...ARRRGH!

Thanks again,
Merv

This is par for the course for include files with thing such as the C language.

all of LTSpice's default devices (i.e. LTxxxx op amps, etc) are in the files LTx.lib, which are binary libraries and can't be edited. anything not in these libraries must be included as an .INC directive or be linked to

interesting, i just found a schematic i built using subs and symbols i created without having to include the subcircuits.... it's been about a year ago i created them.... let me find out how i did it....

ok, it seems i created an .asc file in the main directory, and an .asy file in the /sym directory. the with the same name (i.e. i_pump.asc, i_pump.asy). the .asc file has to be in the form of a regular schematic, not a .sub format (which uses a different format for listing the circuit nodes).

HTH if you know how to write an .asc file that duplicates what is in the .sub file, you can insert it in the schematic without an .INC directive.

i highly recommend you join the LTSpice yahoo group, there are a lot of resources and tutorials there for this kind of stuff

Hi All

Thank you for the responses. They led me to a solution along with some luck on the side.

It seems there are two symbol attributes (SYMATTR) missing in the .asy files of those devices that require the addition of the include directive. When all five symbol attributes are present, in the correct order and with the correct syntax they work just like the resident LT op amp devices. It takes less than 3 minutes to accomplish, even when ones spouse is chatting.

I have changed three devices so far, LM324, LM358 & AD820 (all 5 pin topology), and all work and act just like resident LT devices insofar as general functionallity. I'll start another thread with the proceedure and pitfalls tomorrow or Monday.

Cheers,
Merv