On a schematic diagram of a powered circuit, the power voltage might be labeled Vcc, Vdd, or +V. My question is what do the different voltage designations mean and when does one appropriately use each of the symbols or terms in a circuit diagram?

If you would prefer not to explain and point me to a reference, that would be fine, too.

Searching this site somewhat and in my books, I haven't been able to locate this info, so thanks if you know about it.

Regards,
Pete

 

I think it is mostly institutional, not professional. And it is likely start at school level. The circuits that instructor draws. The circuits in the textbook. Once you get a job, you would be the most junior so you do things the way your superiors (people who will write your evaluation, do you really want to aggravate them?) do.

 

Long before transistors came along B+ was used to indicate the connection to the battery, which made sense.
Then VB would represent the battery voltage. VG is the grid voltage.VA = anode voltage, VK = cathode voltage.

When transistors came on the scene, things started to get confusing.
VB would be the base voltage
VC = collector voltage
VE = emitter voltage.

Then we started to label voltage differences between two pins on the transistor:
VBE = base to emitter voltage
VCE = collector to emitter voltage

So we started labeling the supply voltages as follows:
VBB = base supply voltage
VCC = collector supply voltage
VEE = emitter supply voltage

Then came along the FET (field-effect transistor) with three new terminals, gate, drain and source.
So naturally,
VG = gate voltage
VD = drain voltage
VS = source voltage
VGS = gate to source voltage
VDS = drain to source voltage

VDD = drain supply voltage
VSS = source supply voltage

In summary, when you see VDD and VSS, that usually indicates that the circuit is implemented with FET or MOSFET technology.
When you see VCC and GND, that indicates that the circuit uses BJT (bipolar junction transistors,i.e. NPN and PNP transistors).

 

In summary, when you see VDD and VSS, that usually indicates that the circuit is implemented with FET or MOSFET technology.
When you see VCC and GND, that indicates that the circuit uses BJT (bipolar junction transistors,i.e. NPN and PNP transistors).

Thank you for your post, that is very helpful.

 

You can look at
Vdd as V drain-drain
Vss as V source-source
and Vcc as V colector-collector; The NPN transistor got invented first, so Vcc is usually positive.

You have to watch: Ground, Earth, Common etc. Many times the commons will have labels, like 1, 2 and 3 and eventually they are connected together at one point. it's important to do so, You also have signal ground, digital ground and Analog ground. Signal is usually very clean and used as a reference. Analog ground is also fairly clean. Digital ground is noisy. they are usually decoupled and may be tied together at one point.

 

Usually, when using double-subcripted notation, Vab means Va - Vb, or the voltage at Node A relative to the voltage at Node B. In this framework, a repeated subscript would always be 0 v (Vaa = Va - Va = 0 V). That means that these are available for other uses and, by long tradition, they usually refer to supply voltages. The particular subscript used is implicitly related to a NPN or NMOS circuit so it works out that Vcc and Vdd refer to the positive supply while Vee and Vss refer to the negative supply. You will see lots of circuits that use Vcc/Vee even for FET circuits and Vdd/Vss even for BJT circuits.