Brad Velander wrote:

> Lloyd,
>         I never use the A, K, or E, B, C, conventions myself. I stick to
> numbered pins. Many years ago (on another CAD package) I had seen some
> problems and issues with alpha designated pins and just ran away from them
> as fast as I could go. Today I set out a convention for diodes with pin 1 as
> Cathode or Anode (depends on the CAD system and the company past history)
> and go from there. Same for transistors. In a lot of cases I build special
> diode or transistor symbols just to take care of the myriad of packaging
> options. More symbols in the library to manage but it avoids some of the
> stupid wrong symbol, wrong footprint problems with discrete semi devices.

UGH!  THe problem is there is no standard on transistor packages for which
pin is 1,2,3.  There are so many different packages.  Also, there is no standard

for the E,B,C order.  When you have two things that are both not locked to
some standard, it gets pretty confusing.  Now, if you rigorously create a
schematic part and a PCB part for each component, so that if you have
200 standard transistors you use, you also have a matching set of 200
schematic components and 200 PCB footprints that have matching pin numbers,
that will work reliably.  But, when you select a schematic part, it is possible
to specify one that can be bought in several different packages.  This is where
it gets confusing.  I use the EBC (or GDS) pin label, generally cause the
part to display the pin labels as an assurance that the schematic part will
those alpha labels to the netlist, and then use a modified PCB footprint that
the pins labeled with the appropriate alpha names.

I find, at least for the way I do things that I end up having to twist
leads a lot less with this approach than with the numeric method.


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