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In Reply to: RE: Any scope photos of different resistors... posted by rick_m on December 26, 2014 at 07:45:15
Hello Rick. Do you happen to know ofa sources describing excess noise in detail? I seem to recall that excess noise is voltage dependent but at line levels probably insignificant whereas at speaker signal levels perhaps a factor...Plenty out thee about shot, thermal, popcorn etc but not much describing "excess". Maybe I'm just using the wrong keyword in my searching.
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"Excess noise" is simply everything else beyond the (4kTRB)^1/2 thermal noise voltage.
It's just of a way of thinking about noise and keeping score. You can't avoid the thermal noise but you can work on the noise in "excess" of that such as the crud from micro-arcs in carbon comp. resistors.
Regards, Rick
Ah. Your wording helps clear up a lot for me. It makes sense that micro arcing would be more pronounced with technologies using a depositing or sputtering process to form the conductive paths. I suppose it's difficult to really characterize this problem generally since it must have much to do with specific manufacturing process and materials.
Very interesting. Thanks for the explanation. I'd previously come across a fellows webpage briefly mentioning "contact" noise within conductors/ resistors etc. caused from micro arcing from voids and impurities. One co-worker/mentor of mine has used the term "Excess noise" and didn't explain it to me. Good to finally sort of tie these loose ends into a slightly neater bundle.
Why would micro arcing be more pronounced when the film is deposited by sputtering or perhaps evaporation?
Lots of variables in process design using those processes and enough equipment variation between manufacturers to keep things interesting.
I've used CHA evaporators and Varian sputtering systems.
Link provided so you can see a sputtering system for 6" silicon wafers.
Too much is never enough
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