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When do we use Vcc / Vdd / Vss / V+

Discussion in 'Electronic Basics' started by Guest, Aug 11, 2003.

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  1. Guest

    Guest Guest

    There seems so many symbols for the same thing
    (except that Vss is GND I think) but when do we
    use which ?
  2. As a young person, the history behind those names seems incredibly baffling
    (or stupid, not sure which). People have wondered about it before; you
    might search Google Groops to try to make sense of it yourself.

    Regardless though, Vcc refers to a common positive supply of bipolar ICs (no
    doubt related to a collector). Vdd refers to the common positive supply of
    CMOS circuits (no doubt related to a drain). Vss refers to a common ground
    (no doubt related to a source and therefore CMOS as well). Vee is used to
    refer to a negative supply (no doubt related to an emitter). Since CMOS is
    the most common technology today, if you use Vdd and Vss to describe your
    supplies you will most likely have your symbology right (although anyone
    would understand you if you got it wrong, so long as you used the right
    equivalent). To be the least ambiguous (and to work towards the elimination
    of symbols which don't seem to make any sense), it might be best to refer to
    signals as +5V or +3.3V and GND.

    Howard Henry Schlunder
  3. cpemma

    cpemma Guest

    Take a tip from the Europeans (resistors, caps, etc) and use 3V3 & 1V5 ;-))
  4. Some capture tools don't like leading numbers. I don't think
    this is as bad as them not allowing a '-' in front of signals,
    but I can use only what they allow.

    Though, even VHDL is lacking a standard way of differentiating
    negative active signals. BAD! BAD!
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