Should supply rails be negative?

Huh??

--
"Design is the reverse of analysis" 
                   (R.D. Middlebrook)

Actually, in automobiles, it seems to have occurred when radios went transistorized. I don't know if there's a correlation or not. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Well, everyone deserves the benefit of doubt, even those who don't give it to others. It was worth a shot.

Yes, obviously. The problems with running high-side n-channel switches are relatively minor, and there are well-established solutions. But it is annoying to think that there might be an easier way to do things and only convention prevents it.

The popularity of N-type transistors is understood. What I don't get is how that associates with preferring a positive rail, when to me it seems like N-types would be more practical with a negative rail.

Yes, of course. What else?

A big part of learning about a system is studying different configurations and trying to understand how they behave. It is essential that the configurations are highly variable and illustrate all aspects of the system, and not merely constrained to those encountered in practice.

For instance, when studying physics, it is quite on par to consider what happens when you send someone to space and back at light speed. It doesn't matter that this sort of thing will never ever happen in the real world: it illustrates how special relativity works, and you _have_ to be able to explain what happens if you want to claim to understand physics.

However, in many online discussions of electronics I have seen something that I hesitatingly call an "engineering mindset": if a question is not related to a practical real-world problem that someone is trying to solve, it is not worth discussing. Those sort of people will no doubt think that discussion of unconventional rail configurations is a waste of time. (Those people also must think I'm mad for getting joy from getting a circuit work purely in simulation even if I have no intention of ever building it in practice.)

For comparison, suppose a beginning math student just learned about numeral systems and exclaimed: "Hey, wouldn't it be better if we used a duodecimal system? After all, we divide things into threes and fours much more often than into fives!" A reasonable response would be something like: "Probably, yeah. It's not going to happen, of course, but you are right that it would have advantages." Even though the proposal is utterly unrealistic, making it demonstrates that the student has grasped something essential about the purpose of numeral systems and the tradeoffs in their design, and that is to be commended.

People with an "engineering mindset" would respond: "You're not experienced enough to challenge such basic practices. Keep on using the decimal system like everyone else."

Indeed. Thanks for your reply, the first decent one I got in this thread.

Lauri

Of course. Paul Schoen has been long known to be a nutcase. You and he should pair up >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

;)

The best reasons to keep the current convention are that it works satisfactorily, everybody uses it, and it confuses nobody AFAICT.

Changing would break all three of those fine properties, as well as requiring all the textbooks to be rewritten and all the classical papers changed. That earthquake would make ROHS look like a small bump in the road.

Apart from the Hall effect, there's really nothing going on in solid state circuits that depends on the polarity of the carriers anyway. Electron mobility is higher, but that won't even enter the consciousness of somebody who's likely to have trouble with conventional current flow.

If we were still using tubes, where there's a much more substantial asymmetry, the argument would be a bit stronger but not much.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Well, we're in the business of building things. Lots of things. 95% of what we do works fine without a lot of introspection. The sort of thing that you're talking about, related to the reverse electron current flow convention, most EEs have thought about and got over long ago.

Those sort of people

Most of us will use any power supply arrangement that works. But given that nearly all digital logic chips have multiple positive rails, and the most convenient power switches are low-side n-types, most supplies tend to be positive against common. 74 series TTL exploited fast NPN transistors and pretty much solidified positive logic levels and rails.

Simulation is fun, but so is soldering. Copper as art:

More likely we'd say "bases of 2^n, like hex, are more useful in practise." Nobody (that I know of) does logic or signal processing, in uPs or FPGAs, in decimal. We do lots of - signed and unsigned - binary integer, fixed-point, and fractional formats, and occasionally floats [1]. We'll use 18 bit signed fractional data paths in an upcoming signal processing app. Engineers aren't (all) as inflexible as you seem to suggest. But we've got past most of the basic issues.

[1] somebody semi-famous said "If you absolutely have to use floating point, you don't understand the problem."

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

It really confuses people who learned "electron flow" in the military or in certain trade schools.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

OK that's also the answer I got from here,

7

To quote from one response,

More:

explanation to this question comes from a 1978 Rolls-Royce Enthusiasts' Clu b service manual.

"...it has been found that cars wired positive earth [ground] tend to suffe r from chassis and body corrosion more readily than those wired negative ea rth. The reason is perfectly simple, since metallic corrosion is an electro lytic process where the anode or positive electrode corrodes sacrificially to the cathode. The phenomenon is made use of in the "Cathodic Protection" of steel-hulled ships and underground pipelines where a less 'noble' or mor e electro-negative metal such as magnesium or aluminum is allowed to corrod e sacrificially to the steel thus inhibiting its corrosion."...

For more information on cathodic protection, please read Roger Alexander's article, An idiots guide to cathodic protection or Chris Gibson's article W hat is Galvanic Erosion, is it serious and can it be prevented? for metal b oat hulls. By 1956, all the North American manufactured cars and trucks, ex cept the Metropolitan, were using negative earth [grounding].

Also:

"In most modern automobiles, the grounding is provided by connecting the bo dy of the car to the negative electrode of the battery, a system called 'ne gative ground'. In the past some cars had 'positive ground'. Such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge."

George H.

Put a plus voltage on the cathode and you get a plus voltage on the anode - that arrow thing pointing to where the plus voltage goes..

But then if you cut your teeth on vacuum toobs, it seems unreal that electrons boil off the heated cathode and travel to the anode (or plate) against the logical flow.

But today we are faced with some people using "pins" when they don't mean physical pins but IO ports, or storage drives that are physical or virtual.

In balance the whole concept would seem to strengthen the idea of thinking outside the box, or thinking with no box.

Never argue with empirical results. Adapt.

In diodes and bipolar transistors, *conventional current* "goes with the arrow", NOT electrons.

Voltage does not "go" anywhere, it just sits.

--
"Design is the reverse of analysis" 
                   (R.D. Middlebrook)

That's just to keep "other ranks" "in their place" ;-)

--
"Design is the reverse of analysis" 
                   (R.D. Middlebrook)