small planet

[Magnus Danielson]

From: Martin Czech <czech at Micronas.Com>
Subject: small planet
Date: Thu, 20 Apr 2000 15:26:20 +0200 (MET DST)

> The world is a small planet. The LDR book is still on my desk, a
> colleague walks in, he sees the book and tells me that he worked for
> Valvo in another life and that he edited this very book!
> 
> Now to my question.
> 
> We often see supply pins labeled with Vcc,Vee,Vss,Vdd.  I believe that
> the indices mean collector, emitter, source and drain.  I believe that
> the writers/artists have npn or nmos transistors in mind when labeling
> drawings with this, So Vdd and Vcc means positive supply, Vee and Vss
> negative. This can be different for PMOST-techologies (BBD). But nobody
> told me so, and I have never seen a text saying so.
> 
> Is this so?  Who invented this notation?
> 
> People start to mix it up, I've seen Vee and Vdd together , which makes
> not much sense for a CMOS chip then.
> 
> Since this is a small world, perhaps anybody knows some of the responsible
> old timers ?

This is a case where once logical notation has been continued due to tradition
even if the technology has changed. Vcc and Vee is logical in all NPN ECL
logic, note here that Vcc is hooked to ground and Vee is hooked to -5.2V.

Also, there was once plenty of NMOS only logic, and the use of Vss and Vdd is
then logical aswell.

Then CMOS kicked in seriously and I guess the terms just rippled over since
there was no good term for positive and negative power supply which was unbound
to the underlying technology.

So, just consider it a bad habbit formed by the need of recognition from
previous families.

Cheers,
Magnus