Parasitic capacitance of SMD resistors and their generated noise...

[pavelm...@gmail.com]

Hello, colleagues
My question is about basic component that we all are working with - resistor, actually SMD 0402 type of them.
There are few technologies on the market to make them - thick film, thin film, metal film, and probably some more.
Resistors produced by different technologies has different performance.
Currently I am interested in three characteristics for 0402 size of resistors - parasitic parallel capacitance, parasitic series inductance, and generated noise, and their repeatability/stability/predictability in production. I am talking about frequency range from DC and up to 2 GHz.
Could you provide/reveal values of these properties of 0402 resistors made by each of above technologies? Any additional information will be appreciated.
Thank you

 

[Jeroen Belleman]

On 2022-03-07 12:10, pavelm...@gmail.com wrote:

Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you

I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

 

[server]

On Mon, 07 Mar 2022 12:50:45 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

The parasitics of various resistors are easily googled.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

High tempco resistors in a voltage divider or equivalent can make low
frequency (subsonic) noise from small temperature fluctuations.



--

I yam what I yam - Popeye

 

[Phil Hobbs]

Jeroen Belleman wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Yup. Cermet, thick film, and anything with carbon in it are disastrous
for 1/f noise. They\'re all pretty well equivalent at high frequency.
(\"Thin film\" is SMT-speak for \"metal film\".)

JL made some TDR measurements of (iirc) thin film resistors and showed
that the inductance was significantly reduced by mounting them upside
down, so that the resistive track was next to the board.

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

 

[Rick C]

On Monday, March 7, 2022 at 11:38:54 AM UTC-5, Phil Hobbs wrote:

Jeroen Belleman wrote:
On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman
Yup. Cermet, thick film, and anything with carbon in it are disastrous
for 1/f noise. They\'re all pretty well equivalent at high frequency.
(\"Thin film\" is SMT-speak for \"metal film\".)

JL made some TDR measurements of (iirc) thin film resistors and showed
that the inductance was significantly reduced by mounting them upside
down, so that the resistive track was next to the board.

The inductance or the impedance? If the resistive layer has a smaller spacing from the board it would also impact the capacitance to the ground layer greatly impacting the impedance, probably much more than just the inductance.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Mon, 07 Mar 2022 12:50:45 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

The parasitics of various resistors are easily googled.


Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

As Kipling\'s Shipwrecked Mariner said to the Whale, \"Not so, but far
otherwise.\" (At least in my business, i.e. ultrasensitive measurements,
that is.)

One time I was chasing my tail for about a day, trying to figure out why
my shiny new super low noise laser driver gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.

High tempco resistors in a voltage divider or equivalent can make low
frequency (subsonic) noise from small temperature fluctuations.

Yup. Random temperature drift has roughly a 1/f**2 noise PSD.

The LIGO folks published a study on noise in resistors, IIRC, but I\'m
not laying my hands on it at the moment.

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

 

[server]

On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 07 Mar 2022 12:50:45 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

The parasitics of various resistors are easily googled.


Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

As Kipling\'s Shipwrecked Mariner said to the Whale, \"Not so, but far
otherwise.\" (At least in my business, i.e. ultrasensitive measurements,
that is.)

One time I was chasing my tail for about a day, trying to figure out why
my shiny new super low noise laser driver gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.

Was there voltage across that terminator? Was it making unusually
large amounts of Johnson noise?



--

I yam what I yam - Popeye

 

[server]

On Mon, 7 Mar 2022 11:38:41 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Jeroen Belleman wrote:
On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Yup. Cermet, thick film, and anything with carbon in it are disastrous
for 1/f noise. They\'re all pretty well equivalent at high frequency.
(\"Thin film\" is SMT-speak for \"metal film\".)

JL made some TDR measurements of (iirc) thin film resistors and showed
that the inductance was significantly reduced by mounting them upside
down, so that the resistive track was next to the board.

Cheers

Phil Hobbs

Regular cermets, but the geometric effects are the same.

You can buy resistors without wrap-around end caps, intended to solder
element down.



--

I yam what I yam - Popeye

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 07 Mar 2022 12:50:45 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

The parasitics of various resistors are easily googled.


Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

As Kipling\'s Shipwrecked Mariner said to the Whale, \"Not so, but far
otherwise.\" (At least in my business, i.e. ultrasensitive measurements,
that is.)

One time I was chasing my tail for about a day, trying to figure out why
my shiny new super low noise laser driver gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.


Was there voltage across that terminator? Was it making unusually
large amounts of Johnson noise?

Yes, I was pumping a couple of hundred milliamps into it. 1/f noise
arises from conductance fluctuations, so it doesn\'t appear unless
there\'s current flowing. As you say, Johnson noise depends only on the
resistance and the temperature, but of course it also assumes thermal
equilibrium, which stops applying when the power gets turned on.

Cheers




--
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

 

[Gerhard Hoffmann]

Am 07.03.22 um 16:31 schrieb jlarkin@highlandsniptechnology.com:

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

High tempco resistors in a voltage divider or equivalent can make low
frequency (subsonic) noise from small temperature fluctuations.

I have a version of Win\'s AOE3 ribbon microphone amplifier,
not differential but only single-ended with an ugly coupling cap
and 16 transistors instead of 64.

That has a switchable ~6 Ohm resistor to get \"calibration noise\".
It is easy to see.

<
https://www.flickr.com/photos/137684711@N07/44311358915/in/album-72157662535945536/
> and left / right arrows

My 10 * 2 * ADA4898 amplifier uses 60R as a 1nV/rtHz normal.


Cheers, Gerhard

 

[John Larkin]

On Mon, 7 Mar 2022 12:35:32 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 07 Mar 2022 12:50:45 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

The parasitics of various resistors are easily googled.


Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

As Kipling\'s Shipwrecked Mariner said to the Whale, \"Not so, but far
otherwise.\" (At least in my business, i.e. ultrasensitive measurements,
that is.)

One time I was chasing my tail for about a day, trying to figure out why
my shiny new super low noise laser driver gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.


Was there voltage across that terminator? Was it making unusually
large amounts of Johnson noise?

Yes, I was pumping a couple of hundred milliamps into it. 1/f noise
arises from conductance fluctuations, so it doesn\'t appear unless
there\'s current flowing. As you say, Johnson noise depends only on the
resistance and the temperature, but of course it also assumes thermal
equilibrium, which stops applying when the power gets turned on.

Cheers

It\'s probably too late, but it would be interesting to measure the 1/f
noise vs current. It might be square law, namely thermal.

Thinfilms have much lower tempcos than cermets. There could be
micro/localized thermal effects too, like at grain boundaries. Laser
trimming can create horrors.

I found it difficult to measure excess noise in cermets, and it was in
the ballpark of the Johnson noise. These were megohm range values, so
self-heating was negligable.

Then it was hard to find 10M sorts of thinfilms.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[LM]

On Mon, 07 Mar 2022 09:21:55 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Mon, 7 Mar 2022 11:38:41 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Jeroen Belleman wrote:
On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Yup. Cermet, thick film, and anything with carbon in it are disastrous
for 1/f noise. They\'re all pretty well equivalent at high frequency.
(\"Thin film\" is SMT-speak for \"metal film\".)

JL made some TDR measurements of (iirc) thin film resistors and showed
that the inductance was significantly reduced by mounting them upside
down, so that the resistive track was next to the board.

Cheers

Phil Hobbs

Regular cermets, but the geometric effects are the same.

You can buy resistors without wrap-around end caps, intended to solder
element down.
Digikey had several types of resistors.

Carbon combosition
Carbon film
Ceramic
Metal Element
Metal Film
Metal Foil
Thich Film
Thin Film
Wirewound

Last time I checked, there was only thin and thick film. That is not
much of a choice.

 

[Phil Hobbs]

John Larkin wrote:

On Mon, 7 Mar 2022 12:35:32 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 07 Mar 2022 12:50:45 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

The parasitics of various resistors are easily googled.


Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Johnson noise must be the same regardless of the materials.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure. I managed to measure some once, but it
took very high value resistors and high voltages.

As Kipling\'s Shipwrecked Mariner said to the Whale, \"Not so, but far
otherwise.\" (At least in my business, i.e. ultrasensitive measurements,
that is.)

One time I was chasing my tail for about a day, trying to figure out why
my shiny new super low noise laser driver gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.


Was there voltage across that terminator? Was it making unusually
large amounts of Johnson noise?

Yes, I was pumping a couple of hundred milliamps into it. 1/f noise
arises from conductance fluctuations, so it doesn\'t appear unless
there\'s current flowing. As you say, Johnson noise depends only on the
resistance and the temperature, but of course it also assumes thermal
equilibrium, which stops applying when the power gets turned on.

Cheers

It\'s probably too late, but it would be interesting to measure the 1/f
noise vs current. It might be square law, namely thermal.

Nah, definitely linear, and definitely 1/f not 1/f**2. A constant-rate
drift notionally has a spectrum that goes as 1/f**4, and a random-walk
drift (\'brown noise\') goes as 1/f**2. That\'s what you usually see go
away when you put styrofoam on top of the resistor.

It\'s quite possible that the conductivity fluctuations depend on
temperature, but I don\'t recall hearing that mentioned.

Thinfilms have much lower tempcos than cermets. There could be
micro/localized thermal effects too, like at grain boundaries. Laser
trimming can create horrors.

I found it difficult to measure excess noise in cermets, and it was in
the ballpark of the Johnson noise. These were megohm range values, so
self-heating was negligable.

Then it was hard to find 10M sorts of thinfilms.

Well, believe me, this example was the very furthest thing from subtle.

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

 

[Phil Hobbs]

LM wrote:

On Mon, 07 Mar 2022 09:21:55 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Mon, 7 Mar 2022 11:38:41 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Jeroen Belleman wrote:
On 2022-03-07 12:10, pavelm...@gmail.com wrote:
Hello, colleagues

My question is about basic component that we all
are working with - resistor, actually SMD 0402 type of them. There
are few technologies on the market to make them - thick film, thin
film, metal film, and probably some more. Resistors produced by
different technologies has different performance. Currently I am
interested in three characteristics for 0402 size of resistors -
parasitic parallel capacitance, parasitic series inductance, and
generated noise, and their repeatability/stability/predictability in
production. I am talking about frequency range from DC and up to 2
GHz. Could you provide/reveal values of these properties of 0402
resistors made by each of above technologies? Any additional
information will be appreciated. Thank you



I measured parasitic capacitance and inductance for 1206 resistors
and got about 50fF and 500pH. I\'d expect about the same for 0402,
because they have the same shape. Of course, pad layout and trace
width matters, as does the proximity of other conductors. I only
measured 1% metal film resistors.

Common wisdom says that only metal film should be used where noise
matters. I never made comparative measurements. In my field,
resistor cost is relatively negligible, so I tend to use metal
film almost everywhere.

Jeroen Belleman

Yup. Cermet, thick film, and anything with carbon in it are disastrous
for 1/f noise. They\'re all pretty well equivalent at high frequency.
(\"Thin film\" is SMT-speak for \"metal film\".)

JL made some TDR measurements of (iirc) thin film resistors and showed
that the inductance was significantly reduced by mounting them upside
down, so that the resistive track was next to the board.

Cheers

Phil Hobbs

Regular cermets, but the geometric effects are the same.

You can buy resistors without wrap-around end caps, intended to solder
element down.
Digikey had several types of resistors.

Carbon combosition
Carbon film
Ceramic
Metal Element
Metal Film
Metal Foil
Thich Film
Thin Film
Wirewound

Last time I checked, there was only thin and thick film. That is not
much of a choice.

To an engineering approximation, all metal / \'thin film\' resistors
exhibit only Johnson noise.

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

 

[pavelm...@gmail.com]

On Monday, March 7, 2022 at 1:10:33 PM UTC+2, pavelm...@gmail.com wrote:

Hello, colleagues
My question is about basic component that we all are working with - resistor, actually SMD 0402 type of them.
There are few technologies on the market to make them - thick film, thin film, metal film, and probably some more.
Resistors produced by different technologies has different performance.
Currently I am interested in three characteristics for 0402 size of resistors - parasitic parallel capacitance, parasitic series inductance, and generated noise, and their repeatability/stability/predictability in production. I am talking about frequency range from DC and up to 2 GHz.
Could you provide/reveal values of these properties of 0402 resistors made by each of above technologies? Any additional information will be appreciated.
Thank you

Hello, Everybody
I am excited to read the discussion about the influence of resistor technology on noise. It is very interesting and helpful.
Though one of the original questions was about how 0402 resistor\'s parallel capacitance depends on the resistor\'s technology. Vishay\'s application paper (freqresp.pdf) talks about comparison of thin film resistors with different termination styles (wrap, flip ship) and their capacitance. But they are all made with thin film technology.
They mentioned that for thin film \"normal\" 0402 resistors with wrap termination this C may be expected to be about 40fF. This is, of course, the resistor\'s own parasitic C, as I would like to believe, without taking into account the PCB and pads.
Does anybody of you have a similar number for a comparable thick film 0402 resistor with wrap terminals? I couldn\'t google it, to my surprise.
Thank you for your responses

 

[whit3rd]

On Monday, March 7, 2022 at 11:47:16 AM UTC-8, Phil Hobbs wrote:

John Larkin wrote:
On Mon, 7 Mar 2022 12:35:32 -0500, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

jla...@highlandsniptechnology.com wrote:
On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

...gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.

It\'s probably too late, but it would be interesting to measure the 1/f
noise vs current. It might be square law, namely thermal.

Nah, definitely linear, and definitely 1/f not 1/f**2. A constant-rate
drift notionally has a spectrum that goes as 1/f**4, and a random-walk
drift (\'brown noise\') goes as 1/f**2.

Carbon resistors are semi-metals, so they get recombination noise; probably
the \'cermet\' is a similar material. For metal film, though, it\'s terribly difficult to
get a thin and long continuous metal path for high resistance, AND keep it from
oxidizing and changing value. So, carbon (carbon film?) still is the solution for high-ohms
items.

 

[John Larkin]

On Mon, 7 Mar 2022 13:09:19 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

On Monday, March 7, 2022 at 11:47:16 AM UTC-8, Phil Hobbs wrote:
John Larkin wrote:
On Mon, 7 Mar 2022 12:35:32 -0500, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

jla...@highlandsniptechnology.com wrote:
On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

...gizmo was exhibiting horrific
1/f noise on the spectrum analyzer. It turned out to be the classic
Tektronix 50-ohm 2-W BNC feedthrough terminator I was using--it was made
of cermet. Switching to metal film dropped the 1/f noise by about two
orders of magnitude IIRC. Not subtle at all.

It\'s probably too late, but it would be interesting to measure the 1/f
noise vs current. It might be square law, namely thermal.

Nah, definitely linear, and definitely 1/f not 1/f**2. A constant-rate
drift notionally has a spectrum that goes as 1/f**4, and a random-walk
drift (\'brown noise\') goes as 1/f**2.

Carbon resistors are semi-metals, so they get recombination noise; probably
the \'cermet\' is a similar material. For metal film, though, it\'s terribly difficult to
get a thin and long continuous metal path for high resistance, AND keep it from
oxidizing and changing value. So, carbon (carbon film?) still is the solution for high-ohms
items.

I have some 1T ohm surface-mount cermet resistors.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Phil Hobbs]

whit3rd wrote:

On Monday, March 7, 2022 at 11:47:16 AM UTC-8, Phil Hobbs wrote:
John Larkin wrote:
On Mon, 7 Mar 2022 12:35:32 -0500, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

jla...@highlandsniptechnology.com wrote:
On Mon, 7 Mar 2022 12:03:17 -0500, Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

...gizmo was exhibiting horrific 1/f noise on the spectrum
analyzer. It turned out to be the classic Tektronix 50-ohm
2-W BNC feedthrough terminator I was using--it was made of
cermet. Switching to metal film dropped the 1/f noise by
about two orders of magnitude IIRC. Not subtle at all.

It\'s probably too late, but it would be interesting to measure
the 1/f noise vs current. It might be square law, namely
thermal.

Nah, definitely linear, and definitely 1/f not 1/f**2. A
constant-rate drift notionally has a spectrum that goes as 1/f**4,
and a random-walk drift (\'brown noise\') goes as 1/f**2.

Carbon resistors are semi-metals, so they get recombination noise;

Not sure what you mean by that, exactly. To get recombination noise you
need minority carriers, no?

> probably the \'cermet\' is a similar material.

Cermets aren\'t homogeneous--as the name implies, they\'re ceramic/metal
composites.

For metal film, though, it\'s terribly difficult to get a thin and
long continuous metal path for high resistance,

Why so? I used to make conducting films of 100 angstroms or so. Atoms
are pretty small, and using sputtering as opposed to directional
evaporation will make the film follow even rough substrates pretty well.

AND keep it from oxidizing and changing value. > So, carbon (carbon
film?) still is the solution for high-ohms items.

It\'s certainly true that it\'s harder to make very high resistances out
of very low resistance materials, and there are lots of low-precision
applications where 1/f noise is not a serious issue--overvoltage
protection, for instance.

However, carbon resistors are seriously nonlinear at high voltages--the
resistance of old style Allen-Bradley carbon comps was allowed to drop
by a quarter at their upper voltage limit.

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

 

[Phil Allison]

jla...@highlandsniptechnology.com wrote:
================================

Johnson noise must be the same regardless of the materials.

** A simple fact overwhealmed by persistent myth to the contrary.

Thick-film resistors can have excess noise if there is voltage across
them, but it\'s hard to measure.

** No it isn\'t.

I managed to measure some once, but it
took very high value resistors and high voltages.

** Drivel.

Easy enough to characterise carbon film, carbon comp, metal glaze & MF types with values of say 100K and few DC volts.
JL does not underdstand audio.


....... Phil

 

[Phil Allison]

Phil Hobbs wrote:
==============

However, carbon resistors are seriously nonlinear at high voltages--the
resistance of old style Allen-Bradley carbon comps was allowed to drop
by a quarter at their upper voltage limit.

** Really ????
That is massively ambiguous.

CC resistors can drop in value if they run hot and over time.
Mostly they slowly drift high, over a period of decades.

Crazy to crazy that \" non linearity\".


...... Phil