On Sunday 27 December 2009 04:11:57 DJ Delorie wrote: > I took the time to document my ideas about heavy vs light symbols and > the pin mapping problem: > > http://www.delorie.com/pcb/component-dbs.html > http://www.delorie.com/pcb/pin-mapping.html > At first, let me thank DJ for writing it all down. I just wonder, how flexible this pin mapping could be. Maybe i missed it, but I haven't seen a reference to something I'd call global gate swapping. I better describe what I mean by that term for lack of better words: Especially with OpAmp designs I often end up with dropping a bunch of generic OpAmps first and replace them later in the design process with parts better suited to the job. Something along the lines of "just throw a couple 741s in" and later saying "hmm, this high impedance mic input would call for an OpAmp with JFET input stage" plus replacing with some TL074. Some time later still, one might say "oh well, I better decouple those four OpAmps, let's switch to 2x TL072", again replacing some symbols. Somewhere in between when replacing four 741s with one TL074, there were two power pins left orphaned and two missing by accident and desaster is ready to strike. So, is there a sensible way to leave decision actual packages and relations between symbols and packages open until some later time? I'd imagine something like a generic and extensible symbol "OpAmp" (might be extended with dedicated power pins, compensation capacitors, offset trimming, remarks on needed capabilities like JFET input, precision, low noise, chopper, younameit) and a part providing a set of, say, two Opamps with compensation in a 14-pin SOIC and another part providing four OpAmps in a 14-pin DIP plus some clever way to determine what OpAmp to put into which package (clearly to be overridden by the user). As i see it, such a way would be somewhat conflicting with the current way of slotting symbols and providing refdeses based on order of entry because later changes of mapping between symbols and actual parts, those refdeses will inevitabely be mixed up really bad. Wuould something like that be possible?? Greetings, Florian
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