The currant situation is here:
As it happens, forestry has been "pining" for the removal of currants, because of this stuff.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
It isn't that kind of law, and the devices that deviate from it (such as transistors and diodes) aren't people, nor liable to arrest.
-- Bill Sloman, Sydney
Resistance is futile, while Impedance can store energy and fight back later.
I'm sure people with only 2 contacts have been arrested.
NT
It's only reactive impedance that can store energy. Resistive impedance can only dissipate it, but it can get too hot to touch in the process.
-- Bill Sloman, Sydney
On a more serious note, Ohm's Law was found by observations of the physical world, and nearly any material will violate it if you take self- heating into account.
Some of the guys on the group here who do super-accurate circuits have said that even with the temperature held constant, there's still a small (tens of PPM?) deviation between perfection and reality.
-- www.wescottdesign.com
Is 2k7 a violetter?
NT
Resistors have voltage coefficients that can cause many-per-cent errors. Thick films can be several hundred PPM per volt, or even worse.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Indeed. In IC design, its difficult to get very low voltage co-efficient resisters.
Polys are absolutely useless for low noise design. Diffusion resisters sit in a well, and look like a fet with large pinch off, but can have quite low
1/f.-- Kevin Aylward
When I was at school, 'Ohm's Law' referred to 'constant temperature'. 'Ohm's Formula' might be a better description for what most of use actually use.
This one is pretty close to what I was taught...
"In metallic conductors at a constant temperature and in a zero magnetic field, the current flowing is proportional to the voltage across the ends of the conductor, and is inversely proportional to the resistance of the conductor."
Cheers
-- Clive
The minimum penalty for a violation is a burned finger.
-- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
Or those that took an unauthorized route around the Wien Bridge.
Jamie
Discharged.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Aren't metal films deposited onto ICs? Metal film on silicon can be a darned fine resistor.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
That's almost true
and is inversely proportional to the resistance
And that's just a definition.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Ohm's "law" is just a definition.
There is some physics behind the proportionality, close enough that we use the "Law" all the time in the real world. Most engineers recognize the situations where the approximation isn't good enough.
Every time we design a voltage divider or an opamp circut we assume that I = E/R where R is a thing that we can buy.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Digipots, and some DACs, are usually made with CrSi or somesuch alloy.
It's an extra step though.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
It defines "resistance".
Every time I design a voltage divider (PS feedback, for example), I take into account the Tc of the resistors. Kinda foolish not to, since it's a large part of the error.
CrSi are very good. Like 10ppm temp co. Very linear.
Sure, but CrSi resistors are only actually available on a few processes that are used for general purpose. Its a luxury that is not available to most ic designers.
Getting a good BiCMOS process is also difficult. Most try their best to target what are referred to as "cmos only", although most of these often have a half decent npn.
-- Kevin Aylward
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