electronics

It is generally the +5v supply to the circuitry...
It is a stupid nomenclature, I belive it goes back to the fact that it is the supply for th collector of the transistors...I may be wrong.

You will also see vss vdd where FETs are involved.
It is just silly if it's +5v or +3v... why not just call it that?

Del

As Del says it is a bit of a silly name to call the voltage rails, especially when transistors can be PNP or NPN and the collector can be in a cascode, or wired as an emitter follwer, or common base etc...

Its a bit like Hertz really... I still prefer the old cycles per second c/s - At least it tells you what it is!!

John.

This is the common collector voltage in a bipolar transistor circuit.

Cheers,

ethobil

Whether some think it is stupid or not the correct nomenclature is VCC for common collector supplies, VEE for emitter supplies, VDD for drain supplies and VSS for source supplies. It has been around for a long time and it works. we often have devices that can operate from +/- 12VCC to +/- 100VCC or more. When dealing with devices that have wide supply ranges it is poor practice to label the node with a specific value so we us the generic +/-VCC and put a supply range in the electrical tables. Some people shorthand to +/-VC or VS or just V but the older convention does give us some indication of the technology inside (When Used Correctly), especially when dealing with complex devices that may have multiple supplies like PWMs or FET drivers where the power stage may be MOS and the small signal stage may not bet. In power switching it is important to know the output driver technology.

So guest, what would you call the supply for a circuit using a mixture of fets, mosfets, bipolar transistors, relays and integrated circuits??

V_CC, V_DD, V_SS, V_EE, or just +12 volts?

I know which one I find more informative!

John.

That's just rubbish..

There is no 'Correct'...who made up the rules of 'correctness'.

What could be less ambiguous than actually labelling rails with their voltage?

Most circuits today have mixed technologies in them ..maybe FETs CMOS and bipolar transistors...maybe even different logic famillies on the same rail...so your assertion doesn't hold up.

It's just plain daft to call it anything other than it's actual voltage. Or for circuit board layout some suitable name like analoge 5v. digital supply RawDC etc where ther maybe rails of the same voltage which need to be separated.

Not only is it stupid it is confusing.... It would be easy for an inexperienced person to connect power the wrong way round....

Del

And another thing....
If you are wiring up a chip and you see vss and vdd... one then has to check up the max ratings to work out which is gnd and which +ve. (or at least I do evan after 40 ish years of electronics.
Who gives a damn what the technology is??? The chip is treated as a balck box with I/O characteristics defined by the IC manufacturer.

Identify yourself guest or risk my catly wrath

Del

I am surprised at your reaction. I have participated in this forum as both a member and a guest for quite some time and have always found you to be one of the more impressive contributors. You have to admit that I correctly used the term "correctly". I was not referring to correct behaviour but a correct method to use something. If you designed a circuit that required a specific sequence of steps to operate you could very well call that the "correct" way to operate the circuit. That being said I do not claim that VCC is the best method to use but it serves its purpose. If a Node voltage is known within some reasonable tolerance you label the node with the nominal voltage but when you have a supply range of +-10 to +-65 for an op amp. do you label it +-65V or +-10V. The convention allows for the supply range to be vary large. I design DC to DC converters and the input voltage range on some of them is from 12V to 50V with 80V transient tolerance. These are often just labeled Vin but they may be labeled with a nominal input voltage of 28V. In designing DC to DC converters it is important to know the output technology of the PWM and/or FET driver. Bipolar outputs are common in some of the high power FET drivers but they often need clamping diodes on the outputs if switching at high speed. MOSFET outputs do not need the the clamping diodes because MOSFETS can conduct in both directions. There many cases where the black box needs to be looked inside - especially when designing rad hard circuitry. MOS and Bipolar technologies react very differently to radiation.

I was PLMNY for awhile and I have not logged in in quite some time but visit regularly as a guest. I got bored with all of the homework questions, the long drawn out discussions that went way off topic, and the masses of responses that were guesses at the originals posters question such as "How to select a capacitor?". The only response a question like that deserves is "we need more information"

Anyhow...whatever...I call it how I see it....If I was teaching a beginner I'd call 5v ...5v and keep it simple. Life is sufficiently complex without calling things by a misleading name...afterall...would I call myself a cat if I were anything but feline?

Del