[John Larkin]

On Sat, 22 Jul 2006 17:52:39 -0400, Phil Hobbs
wrote:

John Larkin wrote:
On Sat, 22 Jul 2006 19:56:18 GMT, Phat Bytestard
wrote:


On Sat, 22 Jul 2006 11:48:12 +0100, Eeyore
. com Gave us:


They fail to mention carbon film which is very widely used.

The entire selling point of the sheet was that they are very low
noise compared to other resistor manufacturing mediums.

Noise in a resistor occurs because resistance mediums are actually
heavily diluted semiconductors. The electrons bang around on their
way through. It's a loose lattice.



In a current flow in metals, electron-lattice interactions tend to
space electrons evenly, so their exit from the resistor is more
regular than a random (Poisson) distribution, so current-modulation
noise is far below the shot noise level you'd get for uncorrelated
conduction. The physically longer the resistor, the better the
smoothing effect. This works less well in non-metal conductors, with a
few exceptions.

That doesn't affect Johnson noise of course; that only depends on the
resistance and the temperature, as required by conservation of energy.

John


Oh, man, this old chestnut again. Of course you're perfectly right,
John, but the effort is doomed because half your audience appears to
think that classical thermodynamics is a matter of opinion. Why don't
we all vote on it and find out how resistors *really* behave?

Cheers,

Phil Hobbs

Phil,

Do metal-oxide thickfilm resistors have shot noise? Any idea how much,
as, say, % of full shot?

John