Vcc Vdd etc

[bearpawz]

Hi all, I have no formal education with electronics.. figured I would ask this question just because its bugging me and I need to know why.

Why are power planes named Vcc Vdd Vss etc... Do the two letters after the V mean anything in particular or is it just an arbitrary way of naming different power planes? At first I thought Vdd might have had something to do with Drain, Vss would have something to do with source how ever most of the schematics I have worked with have them the other way around... (Vdd is + and Vss is -)

Just curious.

[mister_e]

Usually

VCC, V+,B+, VDD are the same... i mean +5,+12,+15 or any + voltage

VSS is Ground

VEE is mostely -5,-12 or else - voltage

BUT i don't know if there's any official name for those 'label'

look at this link

[Melanie]

Usually in IC Datasheet taken as...

Vcc - Voltage Collector Collector
Vdd - Voltage Drain Drain
Vee - Voltage Emitter Emitter
Vss - Voltage Source Source
etc

There is another naming convention that sequentially names power rails in the system... Vaa, Vbb (usually reserved for the Battery Supply), Vcc, Vdd etc.

[AllanL5]

Yup, what Melanie said.

Vcc -- For TTL circuitry, this is the +5 volts which sits on the collector of the bi-polar transistor output circuit.
Vee -- For TTL circuitry, this is the GND which sits on the emitter of a bi-polar transistor output circuit.
Vdd -- For CMOS circuitry (like the PIC) this is the +5 (or +3) voltage that sits on the 'drain' of a MOS-FET transistor output circuit.
Vss -- For CMOS circuitry, this is the GND that sits on the 'source' of a MOS-FET transistor output circuit.

[Luciano]

Positive voltages:
Vcc- Positive supply voltage of a Bipolar Junction Transistor.
Vdd- Positive supply voltage of A Field Effect Transistor

Negative voltages/ground:
Vee- Negative supply voltage of a Bipolar Junction Transistor.
Vss- Negative supply voltage of A Field Effect Transistor.

The letters c,d,e and s originated from the name of the legs of the transistors Collector, Drain, Emitter and Source.

The absolute distinctions between these common supply terms has since been blurred by the interchangeable application of TTL and CMOS logic families. Most CMOS (74HC / AC, etc.) IC data sheets now use Vcc and Gnd to designate the positive and negative supply pins.

The doubled suffix indicates that the voltage is "common", i.e. it is the supply voltage to one or more collectors (in the case of cc) and not just the voltage at a specific collector. Similarily, Vee is a common voltage for all emitters etc.

* * *

Above text from web page:
http://www.techpowerup.com/articles/overclocking/45

[mister_e]

tabarnak! zzzzzzzzzzzzzzzzzzZZZZZZZZZZzzzzzzzzzzzZZZZZZZ!!!

anybody else have more and more details on that

[Melanie]

Isn't that a French-Canadian technical expression? *smiles*

[Luciano]

Make no assumptions, read the datasheet first!
Example VSS is not always wired to ground.

(Sorry if we are boring you Steve).

Luciano

[Demon]

Hi Melanie,

To further what Steve was trying to express, that's French for:

"Thank you very much for the information folks, most graciously appreciated."

It is common to say it the way Steve does in some EXTREMELY remote areas of Quebec, or as we say in civilized areas such as Montreal, "where the hand of man has not yet set foot"...

Robert
:P

[bearpawz]

Wow, Well, very good information indeed. Will certainly help me remember now what power rails go where!

[Melanie]

hmmm... I shall have to try it on the streets of Paris next week...

[mister_e]

HaHa for sure they'll not understand those Quebecers expressions. When we go there, they don't understand us. The funniest is when we ask for some butter... it isn't so complicated... 'beurre'

bah that's just funny! I really love those francais de France


few expressions and translations here
and here