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low noise resistor

What type of resistors are low noise resistors? i am using surface
mount (SMD) resistors. I learnt that there are thick film and thin
film resistors. Which types of SMD resistors have lowest noise? kindly
enlighten on this.
Thanks
Kristo
 
P

Phil Allison

Jan 1, 1970
0
What type of resistors are low noise resistors?


** Wire wound ones are hard to beat.

i am using surface mount (SMD) resistors. I learnt that there
are thick film and thin film resistors. Which types of SMD resistors
have lowest noise? kindly enlighten on this.


** Thin films, particularly metal film types have very low "excess " noise.

Thick film types ( aka cermet or metal glaze) can be very noisy by
comparison.

Be aware that resistor self noise is only a issue where there is significant
DC voltage across the part.

BTW:

All resistors have thermal or Johnson noise, which only depends on their
value and temperature.

En = sq rt ( 4.K.T.B.R )

where

En = rms noise voltage
K = Boltzman's constant = 1.38 exp-23
T = temp in degrees Kelvin
B = measurement bandwidth in Hz
R = resistance in ohms


Eg: for 1000 ohms in a 100kHz band at 20C

En = 1.27 exp-6 volts



........ Phil
 
D

Damon Hill

Jan 1, 1970
0
What type of resistors are low noise resistors? i am using surface
mount (SMD) resistors. I learnt that there are thick film and thin
film resistors. Which types of SMD resistors have lowest noise? kindly
enlighten on this.

Generally, thin film, especially metal film. Vishay's bulk foil
technology is among the lowest, but pricey.

--Damon
 
E

Eeyore

Jan 1, 1970
0
What type of resistors are low noise resistors? i am using surface
mount (SMD) resistors. I learnt that there are thick film and thin
film resistors. Which types of SMD resistors have lowest noise? kindly
enlighten on this.

Most SMD resistors have very poor noise levels.

If you want good noise performance economically use a leaded metal film part or
expect to pay a king's ransom for the SMD equivalent which will also be heard to
obtain.

Graham
 
E

Eeyore

Jan 1, 1970
0
Damon said:
Generally, thin film, especially metal film. Vishay's bulk foil
technology is among the lowest, but pricey.

Yes, dollars per resistor IIRC. Their 'application note' regarding them is the
biggest load of lies I've ever seen published by a serious component
manufacturer btw. It panders to the very worst of the audiophool myths.

For cents you can get a leaded metal film part that will perform essentially
identically in most circuits.

Graham
 
M

Martin Griffith

Jan 1, 1970
0
Most SMD resistors have very poor noise levels.

If you want good noise performance economically use a leaded metal film part or
expect to pay a king's ransom for the SMD equivalent which will also be heard to
obtain.

Graham
BC comps/vishay thin films seem ok
Fig 3
in
http://www.rapidonline.com/netalogue/specs/71-2100e.pdf

the smaller the body, more hissy stuff gets out, something to do with
the 1/(magic smoke) ratio


Martin
 
Most SMD resistors have very poor noise levels.


Where did you get that bit of mis-information? Metal film SMD
resistors
are usually good enough.

The trick to low noise design is mostly a matter of decoupling or
mis-matching the noise sources in a circuit. I've made amplifiers
with 300pV/rt(Hz) input-referred noise and 50 Ohm input resistance,
despite opinions that one could never get below about 0.5nV/rt(Hz)
in a wideband matched system.

And yes, this was at normal room temperature.

Jeroen Belleman
 
H

Helmut Sennewald

Jan 1, 1970
0
Martin Griffith said:
BC comps/vishay thin films seem ok
Fig 3
in
http://www.rapidonline.com/netalogue/specs/71-2100e.pdf

the smaller the body, more hissy stuff gets out, something to do with
the 1/(magic smoke) ratio


Martin

Hello,

Has anybody the details about the measurement conditions of current noise.
Yes I know it's in the IEC60195, but I don't have it. I am only interested
in the frequency band(start/stop frequency). The datasheets of the
resitors don't have this information. This makes the numbers there
not really useful.

Best regards,
Helmut
 
M

Martin Griffith

Jan 1, 1970
0
Hello,

Has anybody the details about the measurement conditions of current noise.
Yes I know it's in the IEC60195, but I don't have it. I am only interested
in the frequency band(start/stop frequency). The datasheets of the
resitors don't have this information. This makes the numbers there
not really useful.

Best regards,
Helmut
Sorry, can't help you with that, probably more of a Win Hill/Tom
Bruhns question
but I found another spec sheet, Panasonic stuff, which I have put here
http://es.geocities.com/mart_in_medina/resnoise.pdf
rather than attempt to find it in the original URL

Fig 14, p12 shows thick versus thin film performance


Martin
 
E

Eeyore

Jan 1, 1970
0
Where did you get that bit of mis-information? Metal film SMD
resistors are usually good enough.

Good enough for what and where's the data ?

Graham
 
F

Fred Bloggs

Jan 1, 1970
0
Eeyore said:
Good enough for what and where's the data ?

Graham

Looks like Google terminated your account for terms of use violations,
damned ill-behaved freak.
 
E

Eeyore

Jan 1, 1970
0
Martin said:
but I found another spec sheet, Panasonic stuff, which I have put here
http://es.geocities.com/mart_in_medina/resnoise.pdf
rather than attempt to find it in the original URL

Esta página no está disponible.

Lo sentimos, pero está página no está
disponible en este momento. Por favor, inténtelo
nuevamente más tarde, o haga una búsqueda
en Yahoo! GeoCities de otras páginas que le

interesen.
 
E

Eeyore

Jan 1, 1970
0
Fred said:
Looks like Google terminated your account for terms of use violations,
damned ill-behaved freak.

You're an IDIOT.

I don't post through Google. Never ever have done.

Graham
 
J

John Larkin

Jan 1, 1970
0
What type of resistors are low noise resistors? i am using surface
mount (SMD) resistors. I learnt that there are thick film and thin
film resistors. Which types of SMD resistors have lowest noise? kindly
enlighten on this.
Thanks
Kristo

They're all about the same. All resistors have identical Johnson
noise. If there's voltage across them, some may have "excess noise",
which should in theory be very small for metal film resistors. I've
tried to measure the excess noise of various expensive (thin film) and
dirt-cheap (cermet and carbon film) resistors, without success; they
all seem the same.

There is one type of excess noise that's real and measurable:
temperature fluctuations changing resistance in a voltage divider,
converting DC to super-low-frequency noise. That would matter in
instrumantation situations, certainly not audio. We sometimes put
covers over tender circuits to keep air currents off.

Most real-life circuits tend to be dominated by inherent signal noise,
or by the semiconductors, or by bad design.

John
 
F

Fred Bloggs

Jan 1, 1970
0
Eeyore said:
Fred Bloggs wrote:




You're an IDIOT.

I don't post through Google. Never ever have done.

Graham

Well how many people have that lame "rabbitsfirendsandidiots" email?
 
F

Fred Bloggs

Jan 1, 1970
0
John said:
There is one type of excess noise that's real and measurable:
temperature fluctuations changing resistance in a voltage divider,
converting DC to super-low-frequency noise.

Right, otherwise known as thermoelectric effect. You can make a pretty
good people detector using that.
 
P

Phil Allison

Jan 1, 1970
0
"John Larkin About Fuckwit TROLL "


They're all about the same.


** A blind man's opinion of the view.

All resistors have identical Johnson noise.


** Yawn ............

If there's voltage across them, some may have "excess noise",
which should in theory be very small for metal film resistors.


** So the trolling, autistic fool has no experience to draw from.

I've
tried to measure the excess noise of various expensive (thin film) and
dirt-cheap (cermet and carbon film) resistors, without success; they
all seem the same.


** A blind man's opinion of the view.

It all looks dark to him.




........ Phil
 
E

Eeyore

Jan 1, 1970
0
John said:
They're all about the same. All resistors have identical Johnson
noise. If there's voltage across them, some may have "excess noise",
which should in theory be very small for metal film resistors. I've
tried to measure the excess noise of various expensive (thin film) and
dirt-cheap (cermet and carbon film) resistors, without success; they
all seem the same.

You can't be doing serious low noise work in that case.

You can even HEAR the difference between top quality and cheap metal film
resistors. It may not be readily measurable though since it tends to be popcorn
style noise.

Graham
 
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