Hi Robert,
?You're absolutely right about the use of the envelope - at least for the last standards I had in hand.? (Bernd, can you check what your copy of the standard says about the envelope?) The standards include many symbols used to build up other symbols - for example, the filament, plate, cathode, and grid; the purpose of the envelope was to show that all these symbols that were drawn belong to one physical package. Imagine a 12AX7 tube drawn without the envelope, interpreting the schematic would be more difficult because the association of the various unconnected symbols would not be as obvious. With a transistor, the symbols are all connected so it is easily interpreted regardless of the envelope symbol and, as I wrote in a previous post (and as you commented) transistors in a multi-component package are drawn without a circle.? In reality the circle is unnecessary since even, say, a BC547 transistor is easily recognized as a single device by its
reference designator.
- Cirilo
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________________________________
From: Robert <birmingham_spider@...>
To: kicad-users@...
Sent: Tuesday, June 12, 2012 8:54 PM
Subject: Re: [kicad-users] Re: Comments About Eeschema
?
Nice. About this way i didnt think yet.
Here the circle is mostly used by old people from the times when
transistors in round thin cans were common. Is also a taste of
nostalgie.
Guilty as charged :).?? Actually I was taught that a transistor with a
ring was a discrete component, whereas without the ring it was part of
an integrated circuit.?? In practice since everything at that time was
hand drawn I think most engineers left off the ring (certainly I did).
Does the "envelope" (to use the IEC term) have to be conducting to
appear on the schematic??? Historically I think most transistors and
valves had non-conducting envelopes (eg OC45, ECC83) but they all had a
ring around them on the schematic.?? It would seem that valves still do
so in the standard (and they would look messy without a ring), but not
all transistors.?? However, a search on the official term "envelope"
reveals S00061 and the seemingly identical S00062, suggesting (since the
document shows primitives, not just complete symbols) it *is* allowed to
place a ring around anything.?? S00064 suggests it's also allowed to use
a dashed outline as in my BS817DS symbol.?? Being an old fogey I'm
minded to stick with the ring in symbols I create as it keeps the
symbols consistent.?? If some young whipper-snapper wants to remove them
they would be free to do so (though I reserve the right to suck air
through my three remaining teeth).
The copy of the standard I found using Baidu is 2001, BTW, so later than
yours.
Regards,
Robert.
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