what is a noisy resistor anyway/

I have read about noisy resistors but what makes then noisy and what exactly is the noise? Thanks, Eric

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Peter Wieck Melrose Park, PA

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The interesting discussion provides an equation for the noise level that has no term for a material characteristic. Then goes on to say that there are quiet and noisy constructions. This seems to me a contradiction which is not resolved!


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Mike Coon

Also, some resistors are only noisy under power (load). The Heathkit Audio Signal Tracer had a NOISE function where it would put about 75 -

100VDC across a resistor using the audio probe and if the resistor was noisy you could hear it...

Handy test on tube sets!

John :-#)#

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John Robertson

That's a really bad article.

All resistors have Johnson (thermal) noise, which is white (i.e. flat with frequency). Resistors of the same value all have the same Johnson noise, but they differ a lot in their low-frequency noise.

Some types of resistor, e.g. thick film, cermet, and carbon film, exhibit large fluctuations in conductance. Those don't cause problems if there's no DC voltage applied, but if there is, the conductance fluctuations turn into noise currents with an approximate 1/f power spectrum.

Because of that 1/f, these types of resistor are very noisy at low frequency when there's DC applied.


Phil Hobbs

Dr Philip C D Hobbs 
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Phil Hobbs

And a 'noisy resistor' is one that has become faulty in that it generates a lot of extra noise. Classic issue with carbon comps.


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