On Thursday, 12 December 2019 22:35:22 UTC, Phil Hobbs wrote:
On 2019-12-12 14:00, wrote:
On Thursday, December 12, 2019 at 1:39:53 PM UTC-5, wrote:
I have read about noisy resistors but what makes then noisy and what
exactly is the noise?
Thanks,
Eric

http://www.resistorguide.com/resistor-noise/

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

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