Capacitors on reels--any tendency for values to cluster?...

[Phil Hobbs]

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

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

 

[Fred Bloggs]

On Monday, February 20, 2023 at 3:03:24 PM UTC-5, Phil Hobbs wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

If they are EIA standard capacitors then they should all be within 0.5% of nominal. They do this so the capacitance is within the spec\'d error band for rated value under all conditions of rated stress it\'s spec\'d for. Of course I may just be making this up, because I know it to be a certainty for resistors and only assume there\'s a similar requirement for capacitors.

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

 

[legg]

On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

The parts are bulk (funneled) before test and taping.

Don\'t buy 5% from anyone offering 2% and expect a
normal distribution.

RL

 

[Clifford Heath]

On 21/02/23 11:36, legg wrote:

On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

The parts are bulk (funneled) before test and taping.

Don\'t buy 5% from anyone offering 2% and expect a
normal distribution.

Interesting. Lemme guess: a bimodal distribution? -5..-2, +2..+5?

Clifford Heath.

 

[Clive Arthur]

On 21/02/2023 01:02, Clifford Heath wrote:

On 21/02/23 11:36, legg wrote:
On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors.  There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce.  If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

The parts are bulk (funneled) before test and taping.

Don\'t buy 5% from anyone offering 2% and expect a
normal distribution.

Interesting. Lemme guess: a bimodal distribution? -5..-2, +2..+5?

Clifford Heath.

Or all 2%.

--
Cheers
Clive

 

[Chris Jones]

On 21/02/2023 7:03 am, Phil Hobbs wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors.  There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce.  If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

Do you put these boards through some sort of test jig in production?

If so, could you make it electronically adjust the resistors at test and
store the settings in EEPROM? You wouldn\'t need a proper digital pot,
just a few steps of coarse adjustment (with some analog switches or even
tristated microcontroller pins) to get from 5% to 2%, though it would be
tempting to make it much better. For low volumes you could do one of
those schemes where an operator cuts off a resistor on some units.

You can get capacitor arrays with NP0 dielectric - I wonder whether the
matching within each unit is better than between separate ordinary MLCCs
- though the datasheet doesn\'t say and it wouldn\'t solve your problem
anyway.

 

[Phil Hobbs]

On 2023-02-21 04:57, Clive Arthur wrote:

On 21/02/2023 01:02, Clifford Heath wrote:
On 21/02/23 11:36, legg wrote:
On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

It would be convenient to be able to use 0.5% resistors and 5%
capacitors.  There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce.  If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster
closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

The parts are bulk (funneled) before test and taping.

Don\'t buy 5% from anyone offering 2% and expect a
normal distribution.

Interesting. Lemme guess: a bimodal distribution? -5..-2, +2..+5?

Clifford Heath.


Or all 2%.

I\'d expect that to be more likely. You can\'t afford much test time for
a part that sells for a fraction of a cent.

I\'ll have to get a few reels and see, I suppose.

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

 

[John Larkin]

On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

Sharp cutoff? That\'s going to be tricky at 7 poles. I like passive LC
filters when feasible; they are less twitchy. Might you make your
filter trimmable somehow? That could be fun.

Pity that switched-cap filters are/were so awful. Seems like someone
could make a thinfilm all-analog programmable filter, but I guess it\'s
not worth the trouble. The monolithic ceramic filters are all up at
outrageous frequencies, not suited for DDS filtering or most of the
real-world signals we work with. All the effort is going into
narrowband wireless where the money is.

It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

You could assign one of your lab lackeys to measure some caps here and
there on a reel or two, and report back here.

We did order a reel of truly custom-brewed caps from Capax, 3.3 pF
N4700, to temperature compensate our instant-start LC oscillators.
That worked great. Maybe they would make you a reel of close-matched
parts.

 

[Phil Hobbs]

On 2023-02-21 11:33, John Larkin wrote:

On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

Sharp cutoff? That\'s going to be tricky at 7 poles. I like passive LC
filters when feasible; they are less twitchy. Might you make your
filter trimmable somehow? That could be fun.

Pity that switched-cap filters are/were so awful. Seems like someone
could make a thinfilm all-analog programmable filter, but I guess it\'s
not worth the trouble. The monolithic ceramic filters are all up at
outrageous frequencies, not suited for DDS filtering or most of the
real-world signals we work with. All the effort is going into
narrowband wireless where the money is.



It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

You could assign one of your lab lackeys to measure some caps here and
there on a reel or two, and report back here.

We did order a reel of truly custom-brewed caps from Capax, 3.3 pF
N4700, to temperature compensate our instant-start LC oscillators.
That worked great. Maybe they would make you a reel of close-matched
parts.

Turns out that in the hundreds of picofarads we can get 1% caps for
reasonably cheap.

The filters are 12-dB transition Gaussians, made with LT1260 triple CFAs
and a THS4631 output stage. I want really blameless performance--less
than 0.5% overshoot, 1% bandwidth accuracy, 4:1 shape factor, ideally <
10 nV noise, good linearity.

The amps all have 1 kV/us slew rates, which helps a lot when you have no
control over what ugly thing somebody\'s going to connect to it.

The idea is to be able to characterize photoreceivers for noise using a
true-RMS meter rather than a scope FFT or spectrum analyzer, and to have
a choice of bandwidths.

Simon is doing a nice box with four of them: 10 kHz, 100 kHz, 1 MHz, 5 MHz.

We really don\'t want to do any tweaking if we can possibly help it.
Going to 10 MHz or higher would probably need LCs, at least for the
higher-Q sections. The current design is three Sallen-Key sections with
equal or nearly equal resistors, and one RC pole on the first stage.

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

 

[John Larkin]

On Tue, 21 Feb 2023 14:40:51 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-02-21 11:33, John Larkin wrote:
On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

Sharp cutoff? That\'s going to be tricky at 7 poles. I like passive LC
filters when feasible; they are less twitchy. Might you make your
filter trimmable somehow? That could be fun.

Pity that switched-cap filters are/were so awful. Seems like someone
could make a thinfilm all-analog programmable filter, but I guess it\'s
not worth the trouble. The monolithic ceramic filters are all up at
outrageous frequencies, not suited for DDS filtering or most of the
real-world signals we work with. All the effort is going into
narrowband wireless where the money is.



It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

You could assign one of your lab lackeys to measure some caps here and
there on a reel or two, and report back here.

We did order a reel of truly custom-brewed caps from Capax, 3.3 pF
N4700, to temperature compensate our instant-start LC oscillators.
That worked great. Maybe they would make you a reel of close-matched
parts.




Turns out that in the hundreds of picofarads we can get 1% caps for
reasonably cheap.

The filters are 12-dB transition Gaussians, made with LT1260 triple CFAs
and a THS4631 output stage. I want really blameless performance--less
than 0.5% overshoot, 1% bandwidth accuracy, 4:1 shape factor, ideally
10 nV noise, good linearity.

The amps all have 1 kV/us slew rates, which helps a lot when you have no
control over what ugly thing somebody\'s going to connect to it.

The idea is to be able to characterize photoreceivers for noise using a
true-RMS meter rather than a scope FFT or spectrum analyzer, and to have
a choice of bandwidths.

Simon is doing a nice box with four of them: 10 kHz, 100 kHz, 1 MHz, 5 MHz.

We really don\'t want to do any tweaking if we can possibly help it.
Going to 10 MHz or higher would probably need LCs, at least for the
higher-Q sections. The current design is three Sallen-Key sections with
equal or nearly equal resistors, and one RC pole on the first stage.

Cheers

Phil Hobbs

To do optical measurement to that sort of precision, what do you use
for the light source?

Here\'s my photodiode calibrator for the ill-fated LAM project.

https://www.dropbox.com/sh/0gsjeh8m94a0nbs/AAC_uLD7aO5QF6Qat6dR2NoFa?dl=0

 

[Phil Hobbs]

On 2023-02-21 15:54, John Larkin wrote:

On Tue, 21 Feb 2023 14:40:51 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2023-02-21 11:33, John Larkin wrote:
On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Hi, all,

We\'re making some 7-pole active lowpass filter boards, primarily to go
into test systems (ours and other people\'s).

Sharp cutoff? That\'s going to be tricky at 7 poles. I like passive LC
filters when feasible; they are less twitchy. Might you make your
filter trimmable somehow? That could be fun.

Pity that switched-cap filters are/were so awful. Seems like someone
could make a thinfilm all-analog programmable filter, but I guess it\'s
not worth the trouble. The monolithic ceramic filters are all up at
outrageous frequencies, not suited for DDS filtering or most of the
real-world signals we work with. All the effort is going into
narrowband wireless where the money is.



It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,
but they\'re expensive and relatively scarce. If we could get a few
reels of 5% caps, we could dork the resistor values to get the right
frequency response, _provided_ that the parts on the reel cluster closer
than 5% in value.

Have any of you folks done any measurements on the consistency of NP0
cap values within a reel?

Cheers

Phil Hobbs

You could assign one of your lab lackeys to measure some caps here and
there on a reel or two, and report back here.

We did order a reel of truly custom-brewed caps from Capax, 3.3 pF
N4700, to temperature compensate our instant-start LC oscillators.
That worked great. Maybe they would make you a reel of close-matched
parts.




Turns out that in the hundreds of picofarads we can get 1% caps for
reasonably cheap.

The filters are 12-dB transition Gaussians, made with LT1260 triple CFAs
and a THS4631 output stage. I want really blameless performance--less
than 0.5% overshoot, 1% bandwidth accuracy, 4:1 shape factor, ideally
10 nV noise, good linearity.

The amps all have 1 kV/us slew rates, which helps a lot when you have no
control over what ugly thing somebody\'s going to connect to it.

The idea is to be able to characterize photoreceivers for noise using a
true-RMS meter rather than a scope FFT or spectrum analyzer, and to have
a choice of bandwidths.

Simon is doing a nice box with four of them: 10 kHz, 100 kHz, 1 MHz, 5 MHz.

We really don\'t want to do any tweaking if we can possibly help it.
Going to 10 MHz or higher would probably need LCs, at least for the
higher-Q sections. The current design is three Sallen-Key sections with
equal or nearly equal resistors, and one RC pole on the first stage.

To do optical measurement to that sort of precision, what do you use
for the light source?

One of two models of LED source, based on either a 7-ns LED ($2) or a
2-ns LED ($50). For simple stuff I usually hang a LED barefoot on a
Highland P400 DDG, then dork the pulse height to get the right brightness.

Our LED source boxes are coming out Real Soon Now, with a BNC, a wall
wart, mounting flanges, laser-inscribed case, perspulex running boards,
ion drive, et cetera et cetera.

Inside, they\'re a 74AC14 driving one of the magic fast LEDs, with an
AP2205 adjustable LDO providing a stable VDD. Subnanosecond edges, lots
of drive, cheap like borscht. That way we get everything out of the LEDs.

The AP2205 is a nice part--an adjustable small LDO with 36V max input,
2% accuracy, and _built-in polarity protection_, all for 15 cents. I
may switch my allegiance from the venerable LP2951.

Here\'s my photodiode calibrator for the ill-fated LAM project.

https://www.dropbox.com/sh/0gsjeh8m94a0nbs/AAC_uLD7aO5QF6Qat6dR2NoFa?dl=0

Nice pastel green color!

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

 

[William Beaty]

On Monday, February 20, 2023 at 5:02:53 PM UTC-8, Clifford Heath wrote:

On 21/02/23 11:36, legg wrote:
On Mon, 20 Feb 2023 15:03:09 -0500, Phil Hobbs
It would be convenient to be able to use 0.5% resistors and 5%
capacitors. There are 2% caps available in most of the range we want,

Back in the 1970s we had several hundreds 10% 1K TH carbon resistors. I measured a couple hundreds and crudely plotted the bins (years before \"spreadsheet\" software was all the rage.) Sure enough, the distribution had peaks at roughly +- 10%, and steps at ~5%. Just as everyone had been saying since the ?1950s?

So, buy a too-high value, and then discard all the +5% capacitors, to create a single gaussian peak?
Heh!

OOoo! Build a highspeed machine which rapidly measures a whole spool, then mechanically extracts all the off-value components. Then next, SELL THE MACHINES. (For a much higher price, also offer the machine which re-spools SMT components, where the originating spool has many positions unfilled.. Hmmm, maybe such products already exist?)

 

[Michael Schwingen]

On 2023-02-21, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

The AP2205 is a nice part--an adjustable small LDO with 36V max input,
2% accuracy, and _built-in polarity protection_, all for 15 cents. I
may switch my allegiance from the venerable LP2951.

That looks like a nice part (the adjustable startup time might be useful),
but I don\'t see anything about reverse polarity protection in the datasheet,
only reverse current protection.

There is a new product announcement for the part which touts reverse battery
protection, but the datsheet is lacking such information.

cu
Michael
--
Some people have no respect of age unless it is bottled.

 

[Phil Hobbs]

On 2023-02-28 09:59, Michael Schwingen wrote:

On 2023-02-21, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
The AP2205 is a nice part--an adjustable small LDO with 36V max input,
2% accuracy, and _built-in polarity protection_, all for 15 cents. I
may switch my allegiance from the venerable LP2951.

That looks like a nice part (the adjustable startup time might be useful),
but I don\'t see anything about reverse polarity protection in the datasheet,
only reverse current protection.

There is a new product announcement for the part which touts reverse battery
protection, but the datsheet is lacking such information.

cu
Michael

Yeah, I see that. I don\'t have any more info either--when they come in
I\'ll try it out.

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