what is a noisy resistor anyway/

Question

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

peterwieck33 · Accepted Answer

Peter Wieck Melrose Park, PA

Mike Coon · Answer

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!

Mike.

John Robertson · Answer

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 :-#)# --  (Please post followups or tech inquiries to the USENET newsgroup)                       John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3           (604)872-5757 (Pinballs, Jukes, Video Games)                                "Old pinballers never die, they just flip out."

Phil Hobbs · Answer

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.

Cheers

Phil Hobbs

tabbypurr · Answer

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

what is a noisy resistor anyway/

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