I am reading up on logic circuits, families and levels because it's fun. I have no formal education in physics, computing or electronics.
For power supplies, sometimes one of the supply rails is referred to as ground (abbreviated "GND") โ positive and negative voltages are relative to the ground. In digital electronics, negative voltages are seldom present, and the ground nearly always is the lowest voltage level. In analog electronics (e.g. an audio power amplifier) the ground can be a voltage level between the most positive and most negative voltage level.
I know from previous reading, that electricity - at least when it comes to direct current, but perhaps even when it comes to AC? - has a way in ("line"?) and a way out ("neutral" or "ground"? - disregarding for a second the fact that ground also carries current in case of a ground fault).
Again, from previous reading, I know that we work computers by either supplying them voltage or not (or in some circuits a higher voltage and a lower voltage). In any case, it's a choice between one or the other, since that is what we are trying to represent: boolean true or false.
So, what is this "negative voltage"? Is this a figure of speech or can voltage actually have a negative value? The part from the article that I quoted above states in relativistic terms, that "the ground can be a voltage level between the most positive and most negative voltage level" (italic text by me), which makes me assume "yes". But if voltage is electromotive force, how can it be negative? I amusingly imagine a force "sucking" the current backwards. ๐คญ
Explain it to me as if I was five. ๐ถ
Sic. This explanation is clear as day. Thanks!!!
This explanation is good indeed.
Sometimes you design a circuit where the main chip runs on +3.3V reference to the chips ground at 0V, but somewhere in the proces you end up with an extension board that wants 5V below the ground. For easy of use we just call this -5V instead of renaming everything to 0, 5, and 8,3V. Renaming also has the drawback that I like to measure everything reffering to the ground of the main chip. So I personally just don't rename and keep my reference there.
*fixed 8.5 typo to 8.3
Just so I understand.
In your example, let's say we have a power supply that distributes 5v and 8.5v.
The extension board is easy, we just hook it up from 5v to 0v.
For the 3.3v chip, are we wiring it between 8.5v and 5v? So it only sees a 3.3v voltage difference?
Correct.
A good 'at home' example is your computer power supply
Yes. That will give you a 3.5v difference.