On Sunday 23 September 2007 21:13:40 Andy Peters wrote: > On Sep 23, 2007, at 7:40 AM, Dan McMahill wrote: > > Peter Clifton wrote: > >> On Sat, 2007-09-22 at 20:35 +0200, Stefan Salewski wrote: > >>> I think that opamp-1.sym will not be compatible with SOT23-5 > >>> footprints > >>> -- in TI datasheet of OPA656 pin 1 is output for SOT23 package. > >>> Maybe > >>> opamp-1.sym is compatible with SC70-5 configuration, which I have > >>> newer > >>> seen. > >>> > >>> Or opamp-1.sym and opamp-2.sym are only abstract representations > >>> of an > >>> OpAmp, without any relationship to a concrete footprint? > >>> > >>> In any case, there seems to be no symbol in gEDA related to an > >>> ordinary > >>> OpAmp in DIP8 (or SO8) package. > >>> > >>> This may look very strange for new gEDA/pcb users. > >> > >> There are various "heavy" symbols, such as lm741-1.sym. > >> > >> It is a well known problem though, the mapping between a light symbol > >> and a real package is not something which is easily solved. > > > > which is why I'm in favor of a heavy symbol generator for op-amps like > > the one I demonstrated for bipolar transistors. You use a small > > set of > > symbols and then have a text file which is essentially a spread sheet > > that for each actual part number (the full vendor part number > > including > > package code) you give the mapping from symbol pin to the footprint > > pin > > # as well as list the actual footprint. Its pretty simple, you don't > > have to continually wonder if you have the right footprint or right > > pinout, and you only have to maintain a small number of graphical > > symbols. Adding new part number is then a snap. > > > > I'm more and more convinced it is the way to go. > > This is one MAJOR reason to use heavy symbols. > > I'd rather select a part number from a library, knowing that it > always has the correct footprint and vendor part number (or numbers) > every time, rather than go through an intermediate step to match ALL > parts on the schematic with the proper footprints. That's just too > easy to screw up. > Doesn't the "simple symbol + spreadsheet + algorithm = tons of 'virtual' symbols" mechanism provide exactly that functionality in a manner which is very easy to maintain? Peter
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