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

 

[pfjw@aol.com]

On Thursday, December 12, 2019 at 1:39:53 PM UTC-5, et...@whidbey.com 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/

Peter Wieck
Melrose Park, PA

 

[Mike Coon]

In article <63da826d-85c7-4b45-84c7-376d050ff3a7@googlegroups.com>,
peterwieck33@gmail.com says...

On Thursday, December 12, 2019 at 1:39:53 PM UTC-5, et...@whidbey.com 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/

Peter Wieck
Melrose Park, PA

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]

On 2019/12/12 12:05 p.m., Mike Coon wrote:

In article <63da826d-85c7-4b45-84c7-376d050ff3a7@googlegroups.com>,
peterwieck33@gmail.com says...

On Thursday, December 12, 2019 at 1:39:53 PM UTC-5, et...@whidbey.com 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/

Peter Wieck
Melrose Park, PA

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.

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)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Phil Hobbs]

On 2019-12-12 14:00, pfjw@aol.com wrote:

On Thursday, December 12, 2019 at 1:39:53 PM UTC-5, et...@whidbey.com 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

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

On Thursday, 12 December 2019 22:35:22 UTC, Phil Hobbs wrote:

On 2019-12-12 14:00, pfjw@aol.com wrote:
On Thursday, December 12, 2019 at 1:39:53 PM UTC-5, et...@whidbey.com 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