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Please try to explain this in a way that I will understand. This is extremely frustrating for me. And try to explain where my confusion lies. I'll try to explain my frustration.

Every piece of electronics whether it be a microprocessor or LCD screen always has a positive power supply and a ground pin. The positive power supply or VDD is clearly where you supply something like 5 volts. It would be like taking a 5 volt battery and connecting the positive end with a wire to the VDD pin.

But the ground pin is always connected to the "negative" power supply or the negative part of the battery. This would be like connecting the negative end of the same battery to the GND pin.

They conveniently call it the "ground rail" when clearly there's electricity flowing through it. Why is not called the "negative rail"? Ground is supposed to be a reference point. Why call it ground if you're literally connecting it through the circuit? There's no reference point.

Also conveniently, there's never a "negative power supply" pin. Wouldn't it make more sense to have 3 pins, one for the positive side of the battery, one for the negative side of the battery and an actual ground pin which is attached to a piece of concrete? But there's never a true ground pin that's never attached to a battery.

Also, I don't even know if the term "negative power supply" even makes sense. Can it also be called the "anode"? Is it also the "negative part of the battery"? Nothing makes sense anymore. Sorry for my anger, I just can't make sense of this.

I guess you could just try to explain why is the GND pin not called the "Negative power supply"?

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    \$\begingroup\$ See if my answer here is of any help. \$\endgroup\$
    – Transistor
    Apr 14, 2022 at 8:08
  • \$\begingroup\$ It is not "ground" but "common". Ground is the Earth. \$\endgroup\$
    – user263983
    Apr 14, 2022 at 9:56
  • \$\begingroup\$ The telephone system used to use +ve ground back in the day. The supply was -48V. This was chosen because of exciting electrochemical consideration re corrosion of conductors in the damp. \$\endgroup\$
    – Dan
    Apr 14, 2022 at 18:41
  • \$\begingroup\$ It isn't always. Which end of a battery (powering a single-supply circuit) acts as the circuit's reference potential (ground) is a design decision; there is no absolute reference for all applications. Almost all transistor radios produced in the 50's and 60's were "positive-ground", as is the telephone system in the United States. The electrical system in early Volkswagen Beetles was 6 V, and IIEC,positive ground. \$\endgroup\$
    – AnalogKid
    Apr 17, 2022 at 3:19
  • \$\begingroup\$ If you're going to use it as a reference point in the circuit, then is has to connected to the circuit somewhere! \$\endgroup\$
    – brhans
    May 31, 2022 at 11:42

8 Answers 8

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Every piece of electronics whether it be a microprocessor or LCD screen always has a positive power supply and a ground pin.

There's a bit of history to all this. Later, below. There's also an argument for convention. But it's not necessary to go there.

The positive power supply or VDD is clearly where you supply something like 5 volts. It would be like taking a 5 volt battery and connecting the positive end with a wire to the VDD pin.

Again, there's history here. And yes, it can be a bit boggling at first -- why +5 and not -5 as the standard way of looking at things. (One could argue that when we write numbers down, we only add the sign for negative numbers. So is that the reason? No. Not really. It's about history and to a degree also about devices.)

But the ground pin is always connected to the "negative" power supply or the negative part of the battery. This would be like connecting the negative end of the same battery to the GND pin.

Again, the history and devices.

They conveniently call it the "ground rail" when clearly there's electricity flowing through it. Why is not called the "negative rail"?

You can. I have, at times. Depends on the context and who I'm speaking to.

Ground is supposed to be a reference point. Why call it ground if you're literally connecting it through the circuit? There's no reference point.

The circuit and nature has no idea about what you call the ground reference. That's entirely for you, as a human, thinking about things. Nature cares not the least bit about it.

Also conveniently, there's never a "negative power supply" pin.

Well, that's not true. Often, and especially during a specific period of electronics history, if not now, there was a need for bipolar supplies when using opamps. And in these cases there is very often a complementary negative rail. \$\pm 15\:\text{V}\$ was very common in my day. \$\pm 12\:\text{V}\$ or \$\pm 5\:\text{V}\$ not uncommon today.

Wouldn't it make more sense to have 3 pins, one for the positive side of the battery, one for the negative side of the battery and an actual ground pin which is attached to a piece of concrete?

No. It's here that you have conflated two distinct ideas. The battery itself only has two terminals to it: a more negative end and a more positive end. That's all there is.

A piece of concrete with rebar -- a so-called Ufer ground because Dr. Ufer did the research on it in WW II -- or dirt with a copper stake in it is for entirely different purposes. And, it has no connection to the battery and the voltage at the two ends of the battery may have no connection whatsoever to a Ufer ground or a copper stake in the dirt.

But there's never a true ground pin that's never attached to a battery.

That's because you are defining "true ground" as being Earth because you are conflating ideas and haven't yet been able to separate them out in your head. So they are a kind of mush -- all muddled together.

Also, I don't even know if the term "negative power supply" even makes sense. Can it also be called the "anode"? Is it also the "negative part of the battery"?

Yes, the negative terminal of a battery is the anode -- from a chemist's point of view.

Nothing makes sense anymore. Sorry for my anger, I just can't make sense of this.

No problem. You just need to destroy some fixations you have in your head and replace them with some newer, better ideas. That can take time. Sometimes, it only happens "like a shot" where you suddenly have everything dawn on you in a moment's time.

I guess you could just try to explain why is the GND pin not called the "Negative power supply"?

Well, let's get to the history.

  1. Benjamin Franklin famously made a choice that later caused us to say that electrons (once they were discovered) carry a negative charge. In metals, electric currents are motions of (-) charge and so, when thinking about moving particles, we imagine a current that is in an opposite direction to how Franklin imagined things with his resinous and vitreous electricity. (This doesn't mean that we can't have protons moving around -- we can -- for example, in battery acid atoms with extra protons can flow and this flow is a genuine electric current.)
  2. Vacuum tubes have a cathode and an anode. But we understood, because we had to understand at the time, that electrons were "boiled off" of the cathode. Because that's what it takes. (There is also something called "field emission" but that isn't how most such devices worked at the time.) The plate (which is relatively positive) did not need to be heated up to make the device work. There was a choice made, because of what was easier at the time to achieve, to make the vacuum tube cathode (connected to the battery anode) the "reference point" and for the plate voltage to be relative to it. This fact alone forced the idea of a B+ battery voltage, which you will find everywhere in the early literature -- dating well before 1920.
  3. When the transistor was invented, it just happened to be the case that NPN BJTs (for still different reasons) were able to provide better characteristics than PNP. And with common-emitter designs using single-ended signals (cheaper, easier), this meant once again that it was more convenient to reference the signal to the NPN emitter, which just happens to be "more negative" with respect to the "other power supply rail." So, once again, we find ourselves continuing along a path pushing towards keeping the negative end as the "reference."

It's a confluence of history and devices and, as it turns out, some physical fundamentals, as well.

We are here. Get over it and get with the program.

As far as your thoughts about "Earth?" That's an entirely different thing. It's a safety issue with respect to modern AC power delivery to homes and businesses. Most especially, it's about safety with higher voltage AC! And not at all about lower voltage DC issues.

Some DC circuits really do use the (+) rail as their "reference point." If you don't believe me about this, look up ECL, where the positive rail is the ground reference and the other power supply rail is always negative with respect to it.

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    \$\begingroup\$ I believe entirely scrubbing the term Ground in electronic education and replacing it in each instance with a respective more precise term would remove a lot of confusion from people regarding "grounding" in enclosures, PCBs, signals, cables and clear up a lot of the purported EMI "magic" \$\endgroup\$
    – tobalt
    Apr 14, 2022 at 5:35
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    \$\begingroup\$ @tobalt Yes, probably. \$\endgroup\$ Apr 14, 2022 at 10:07
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But the ground pin is always connected to the "negative" power supply or the negative part of the battery. This would be like connecting the negative end of the same battery to the GND pin.

power supply

As you can see with an isolated power supply you can connect ground to either positive or negative or neither.

Also conveniently, there's never a "negative power supply" pin. Wouldn't it make more sense to have 3 pins, one for the positive side of the battery, one for the negative side of the battery and an actual ground pin which is attached to a piece of concrete?

Lots of devices have positive, negative, and ground rails. Positive or negative can be the same as ground on some devices, but "never" is wrong. Pretty common to see equipment for example that runs off of +15, -15 and GND.

I suspect a lot of confusion here is the convention of referring to the negative rail as "GND" even when it is not actually grounded. For example, your phone charge has a USB port with a +5 and GND (negative) wire, but no actual ground connection.

Also, I don't even know if the term "negative power supply" even makes sense.

Usually that refers to a power supply that makes a negative voltage relative to ground (or some other reference).

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Every piece of electronics whether it be a microprocessor or LCD screen always has a positive power supply and a ground pin.

Not really. To drive current into a conventional circuit, you need two circuit nodes for the current to flow through. That's all. How much voltage is between them, and how they are called, depends on the circuit.

The circuits you were playing with usually had a significant voltage between these two nodes, but that's not necessary. There are circuits that, compared to an Arduino or an LCD screen, have almost zero voltage across them, but a large current still flows. Say, a piece of wire, and you want the wire to heat up: lots of current will flow with very little voltage.

The positive power supply or VDD is clearly where you supply something like 5 volts. It would be like taking a 5 volt battery and connecting the positive end with a wire to the VDD pin.

But the ground pin is always connected to the "negative" power supply or the negative part of the battery. This would be like connecting the negative end of the same battery to the GND pin.

It is that way, not "like it". You're not setting up any equivalent ideas here: you're describing exactly how such circuits are connected.

They conveniently call it the "ground rail"

It's a name. It's entirely arbitrary, and how the name came to be is rooted in history. Battery circuits you're building are not grounded at all: they are isolated from Earth!

when clearly there's electricity flowing through it.

Let's distinguish two concepts here:

  1. The ground node - this is a term from circuit analysis. It's an abstract concept: it's not physically realizable. In circuit analysis, a node is one single potential. Currents may flow through the node, but it doesn't change anything, since the node is the equivalent of a superconductor: no matter how much current flows through it, all elements connected to a given node see the same potential at that node.

  2. The ground circuit - this is the real thing you can touch with your finger. The idea is that you want the ground circuit to approximate the behavior of a ground node. So, you connect all the elements to ground using low-impedance connections that act "almost like" ideal shorts, i.e. superconductors, or 0-Ohm resistors.

Why is not called the "negative rail"?

Sometimes it is. The name does not change what it is. Naming things is so that we can refer to them using a common term/word. It has no effect on what those things are or how they act.

Ground is supposed to be a reference point.

And it is. Both in circuit analysis - where nodes are abstract concepts, and act like ideal wires, and in real circuits - where you design them so that the voltage drops across the ground circuit are so low as to not unduly affect the operation of the circuit.

Why call it ground if you're literally connecting it through the circuit?

It's not "connected through the circuit". It is a circuit all of its own, since reality is not ideal, and real ground circuits are full of small-valued resistors, inductors, and such. There are multiple reference points that you could call ground, since they are all in the ground circuit - and you thus need to be careful how you measure things. In the circuit shown below, the biggest impact is due to the battery being non-ideal and having some equivalent series resistance. But even here, if you wanted to measure voltage across the load, you'd have several choices of where to attach a voltmeter, and with a 6.5 digit voltmeter, you'd easily see the differences between e.g. measuring the voltage directly across the battery and directly across the load resistor!

schematic

simulate this circuit – Schematic created using CircuitLab

There's no reference point.

There are multiple reference points along the ground circuit, indeed. See above.

Also conveniently, there's never a "negative power supply" pin.

Of course, there is! It's your choice not to call it that way.

Wouldn't it make more sense to have [...] an actual ground pin which is attached to a piece of concrete?

The non-idealities of an actual Earth connection are so bad that it's almost useless for the purpose you have in mind. A piece of wire is essentially a superconductor compared to a small electrode driven into average soil (neither very dry nor very wet).

Real concrete, extracted from the soil and placed on your bench, in a dry lab, is essentially an isolator. "Connecting" anything to it would imply having megaohm-gigaohm impedances in series with the connection. Given that your multimeter has 10 MOhm input impedance, the multimeter itself would skew the results so much as to be useless.

If you put that concrete slab back into the dirt outside, its conductivity would be rising slowly as it absorbed water from the soil and atmosphere. Eventually, its bulk resistance would be closer to that of a bowl of pudding than a bowl of dry cat food, but neither seems like a better alternative in a laboratory setting.

Wouldn't it make more sense to have 3 pins, one for the positive side of the battery, one for the negative side of the battery and an actual ground pin which is attached to a piece of concrete?

No, because:

  1. The actual Earth connection going into the soil is only useful for dissipating static charges, lightning, and corrosion protection. It's not actually a reference point of any kind. If you actually connected several ground electrodes in a city, and wired voltmeters between them, you'd not be reading anywhere near zero volts!

  2. Real "ground circuits" that we label "GND" in the schematic are meant to have relatively high conductance, and be "close enough" to being ideal that you can often treat them as equipotential, i.e. as if they were a single node in circuit analysis.

  3. The connection between the external Earth and the circuit would still need to be done at a particular point in that circuit. You are choosing that point every time you attach a measurement instrument to the circuit, and it's not true that only one reference point is useful or even should be preferred. It all depends on what the circuit is doing.

  4. Circuits work just fine without any Earth reference whatsoever. Like the mobile device you're most likely reading this answer on. There's really no actual mental connection between "ground node" in circuit analysis and "a 1/2" diameter, 8 ft long copper rod driven into the soil in my backyard".

But there's never a true ground pin that's never attached to a battery.

There is. It is whichever point you choose, because in reality a ground node is fiction. Even in most mundane of breadboard circuits, with good tools you can measure voltage drops across every piece of wire and conductive spring. So, you need to make a conscious choice as to what your reference point is, every time you make a measurement.

Also, I don't even know if the term "negative power supply" even makes sense.

It does, and it's widely used. Just google it.

Can it also be called the "anode"? Is it also the "negative part of the battery"?

Assuming you got no semiconductors in your circuit, that would be perhaps handy, but real circuits have dozens or even billions of various anodes in them, so there would be a problem with which anode you're talking about. Every P-N semiconductor junction has an anode and a cathode...

Nothing makes sense anymore. Sorry for my anger, I just can't make sense of this.

It only doesn't make sense because you think that "Ground" = "Dirt outside my window". It doesn't mean that at all.

The word "ground" as used in technical English of circuit analysis means, almost universally, the node you consider to have a zero potential.

Which node it is is entirely up to you, and real circuits don't have a single ground node: they have many nodes in a real ground circuit that has many non-ideal impedances strewn across it.

I guess you could just try to explain why is the GND pin not called the "Negative power supply"?

Because you chose not to call it that way. It's your choice. Really. Nobody is forcing you, I don't know where this idea came from!

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There is a long history with electronics referring to ‘zero volts’ as ‘ground’, although they mean different things.

‘Zero volts’ really means the common return for all the power supplies in the system.

Ground, more narrowly speaking, is earth ground. In practical use, earth ground is the reference for safety ground, and ties to an earthing terminal at the service feed and in many cases also to a conductor physically connected to the earth with a grounding rod.

When you describe a utility feed voltage, it is expressed with respect to earth ground. So it’s the zero-volt reference for the transmission lines.

An appliance that uses wall power can choose to have no safety ground connection (like a phone charger) or use a grounded case (like a PC, microwave oven, etc.) Devices with a grounded case will often tie their ‘zero volts’ point to the case, that is, safety ground, to control emissions and dissipate static charge.

Stand-alone systems like automobiles can arbitrarily choose a reference for ‘ground’. Almost all vehicles today use ‘negative ground’, meaning the battery (-) terminal is tied to chassis. This hasn’t always been the case: many older vehicles and motorcycles used ‘positive ground’, with battery (+) tied to the chassis. But in neither case is the chassis a true earth ground, but it’s called that because the chassis kind of behaves like an earth ground, as a large, low-impedance plane.

Nevertheless, in electronics we often use the term ‘ground’ as a shorthand for the ‘zero volts return for all the power supplies in the system’, even is if this return isn’t actually tied to a safety or earth ground.

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Ground is just another word for 0 V when speaking of supply rails. It never has to do with protective earth (PE, green/yellow wires, the earth rod) when discussing IC supply rails.

Therefore, datasheets tend to call supply pins "ground" in several cases:

  • the IC has several supplies with a common reference point like processors or mixed-signal ICs
  • the IC is meant to interface with devices that have multiple positive supply rails like little logic
  • for e.g. opamps, you have indeed a positive and negative supply pin and no ground pin. sometimes the negative pin is called ground because it is connected to the IC substrate. But this has no consequence to the user and should be considered an obsolete naming convention.
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The "zero volt" reference is typically called "ground". Audio amplifiers often have "bipolar" power supplies -15v and +15volts and a 0 volt rail that is commonly referred to as "ground". Don't let it bother you, it is just a phrase. The "ground" on other electronics (mains powered or battery), the zero volt is just typically called ground.

To confuse the situation, years ago when germanium PNP transistors were common, nine volt battery radios were on the market where the positive terminal was referred to as ground and the negative terminal was -9 volts (vs ground). Some guitar effects pedals still use this protocol because they use germanium transistors and/or are used in a box with older germanium pedals and the unusual power setup prevents ground loops, shorts, and keeps things consistent.

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Ground or earth could be

  1. a reference point in an electrical circuit, from which voltages are measured, known as 'signal ground'.

enter image description here

  1. a common return path for electric current, known as 'chassis ground'.

enter image description here

  1. a direct physical connection to the ground, known as 'earth ground'.

enter image description here

It is incorrect to assume that 'negative earthing' has always been the only option.

Over the years, it has been either positive earth or negative or both, for reasons such as circuit configuration (PNP or NPN), mitigation of undesirable effects of galvanic corrosion or convention based on convenience.

The result has been, for example, negative-earthed 7812 or positive-earthed 7912 power supplies or dual-power supplies using both regulators with the negative of one and the positive of the other being earthed.

Early automotive electrical systems were positive-earthed to reduce failures caused by anodic corrosion but the convention right now supports negative earthing.

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Every piece of electronics whether it be a microprocessor or LCD screen always has a positive power supply and a ground pin.
...
Also conveniently, there's never a "negative power supply" pin.

In a modern desktop PC, there are not only positive power supplies (+12V, +5V, +3.3V) but also a negative one (-12V).

So your assumption is not correct.

Also, I don't even know if the term "negative power supply" even makes sense.

Sure: The -12V pin in the desktop PC is an example for this.

I guess you could just try to explain why is the GND pin not called the "Negative power supply"?

If you have a circuit without any connectors (and without a metal casing), you might call the power supply pins +5V and -5V if the circuit requires a voltage of 10V.

However, if you say: "The voltage of the signal XYZ is 3V", it means that the voltage between the +5V pin and the pin XYZ is 2V and the voltage between -5V and XYZ is 8V. Although the voltage of pin XYZ is 3V, there is no voltage between XYZ and any other pin that is 3V if there is no "0V" pin.

For this reason, it makes sense to define that the "common" pin (e.g. the common negative voltage for different signals) of some connector is the "0V" (GND) pin.

Early digital circuits used NMOS technology. Because of the way NMOS circuits work, the "common" signal must be the negative pin.

Later on, CMOS circuits were used; using CMOS circuits, it would have been possible to use the positive pin of the battery as "common" signal. However, if you want to be compatible to existing circuits (e.g. using a CMOS and an NMOS IC in the same device), it makes sense to use the negative pin as "common" signal in CMOS circuits, too.

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