Re: gEDA-user: Problems with MOSFET symbols in PCB

[John Doty <jpd@xxxxxxxxx>]

On Dec 17, 2009, at 9:45 AM, Larry Battraw wrote:

>
>    Hi, I've been using gEDA for a little while now and have run into
>    problems using the MOSFET symbols in the library
>    (./gEDA/sym/analog/nmos-3.sym).  When I transfer the changes from
>    gschem to pcb the TO220 footprints I've specified show up fine  
> but I
>    never can make any connections show up as ratlines to the
>    gate/drain/source pins.  I get errors for all pins like so in  
> the log:
>    Can't find S2/Q406 pin D called for in netlist.
>    WARNING! Pin number ending with 'D' encountered in netlist file
>    Probably a bad netlist file format
>    Can't find S2/Q405 pin D called for in netlist.
>    I've attached the netlist for the project to illustrate what's  
> going
>    on.  I have no idea why it would have a problem with it or what to
>    change and even using different MOSFET symbols doesn't fix the
>    problem.
>

The problem is that nmos-3 is a "generic" symbol that doesn't  
represent a MOSFET with a particular footprint. It doesn't even have  
the right number of pins for you: TO220 is a four pin package (the  
tab counts, as it is usually connected electrically). You generally  
need to customize symbols to match your parts and design flow. The  
library author cannot know you are using pcb as your layout program  
(there are many other possibilities), and more importantly, gsch2pcb  
can't read the datasheet to figure out which electrode attaches to  
which pin: you need to supply that information.

Even if the symbol *does* have the right quantity of numbered pins,  
you should check against the physical footprint using the datasheet.  
Different manufacturers sometimes number pins differently, so if the  
footprint is numbered according to manufacturer X's convention, but  
the symbol is numbered according to manufacturer Y's...

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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