4 resistor in one 1206 package: Does their resistance match

S

SioL

Guest
I've noticed 4 resistors are now available in a convenient SMD 1206 package.

Remember how transistors on the same die (like those transistor arrays) used to have
closely matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.

SioL
 
That applies to resistors on an IC. The discrete arrays are often hybrid
circuits where the resistive layer is silk screened onto them. Then it
all depends on the manufacturer. They can laser trim each to whatever
percent they want to. But you'll have to ask them about whether tracking
is better than their absolute tolerance. Usually it isn't.

Regards, Joerg

http://www.analogconsultants.com
 
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:5cLuc.76756$2p3.30292@newssvr25.news.prodigy.com...
That applies to resistors on an IC. The discrete arrays are often hybrid
circuits where the resistive layer is silk screened onto them. Then it
all depends on the manufacturer. They can laser trim each to whatever
percent they want to. But you'll have to ask them about whether tracking
is better than their absolute tolerance. Usually it isn't.

Regards, Joerg
Click to expand...
I don't think we understand eachother. I'm talking about a small 4-resistor (1206 form factor)
package. Not a hybrid circuit. Unless you think the manufacturing process is the same?

I know they're not accurate as far as their common value is concerned, they're mostly designed
for the digital circuits (pull up etc), but all 4 in the package might have the same value.

Just guessing.

SioL
 
"SioL" <spam@spam.com> wrote in message news:<yDHuc.4078$37.501863@news.siol.net>...
I've noticed 4 resistors are now available in a convenient SMD 1206 package.

Remember how transistors on the same die (like those transistor arrays) used > to have closely matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.
Click to expand...
Depends on which array you are talking about, and what sort of
matching you want.

Vishay can probably come up with +/-0.05% ratio tolerances and
+/-2ppm/C TCR tracking, if you go for the right parts.

I looked at something similar a few years ago, and could have got a
single tube of a more or less arbitrary set of values (the resistance
range couldn't exceed 10:1 within the array) for rather less than
$1000.

Farnell stock a restricted set of Vishay precision dividers in the
SOT-23 package which you might find interesting, if you need this sort
of ratio stability.

If you could be more specific about the precison and stability you
need, we might be able to come up with more specific information.

------
Bill Sloman, Nijmegen
 
"Bill Sloman" <bill.sloman@ieee.org> wrote in message
"SioL" <spam@spam.com> wrote in message news:<yDHuc.4078$37.501863@news.siol.net>...
I've noticed 4 resistors are now available in a convenient SMD 1206 package.

Remember how transistors on the same die (like those transistor arrays) used > to have closely
matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.

Depends on which array you are talking about, and what sort of
matching you want.

Vishay can probably come up with +/-0.05% ratio tolerances and
+/-2ppm/C TCR tracking, if you go for the right parts.

I looked at something similar a few years ago, and could have got a
single tube of a more or less arbitrary set of values (the resistance
range couldn't exceed 10:1 within the array) for rather less than
$1000.

Farnell stock a restricted set of Vishay precision dividers in the
SOT-23 package which you might find interesting, if you need this sort
of ratio stability.

If you could be more specific about the precison and stability you
need, we might be able to come up with more specific information.

Bill Sloman, Nijmegen
Click to expand...
Let's just forget this whole thing. Its easier to go out and buy 10-20 and measure
them.

SioL
 
Can you post a URL with a datasheet?

Even the very small stuff I saw was all made on thick film and laser
trimmed. Done a lot of laser trim designs myself and since laser time is
$$$ you usually stop each trim location the millisecond you hit the
required tolerance. Any more trimming adds laser time and reduces
profit. Which means that in this scenario you cannot always guarantee
better tracking than the absolute tolerances are. Usually it is a bit
better than abs tolerance though because the laser always does the same
cut pattern. So if, for example, it would stop at plus 0.9% then the
resistors on that hybrid might all be within 0.1% or 0.2% of each other.
Might, no guarantees. Sometimes the cutting is coarse so the "steps"
between shots are just too much for good tracking.

Regards, Joerg

http://www.analogconsultants.com
 
On Tue, 1 Jun 2004 00:31:41 +0200, the renowned "SioL" <spam@spam.com>
wrote:

"Bill Sloman" <bill.sloman@ieee.org> wrote in message
"SioL" <spam@spam.com> wrote in message news:<yDHuc.4078$37.501863@news.siol.net>...
I've noticed 4 resistors are now available in a convenient SMD 1206 package.

Remember how transistors on the same die (like those transistor arrays) used > to have closely
matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.

Depends on which array you are talking about, and what sort of
matching you want.

Vishay can probably come up with +/-0.05% ratio tolerances and
+/-2ppm/C TCR tracking, if you go for the right parts.

I looked at something similar a few years ago, and could have got a
single tube of a more or less arbitrary set of values (the resistance
range couldn't exceed 10:1 within the array) for rather less than
$1000.

Farnell stock a restricted set of Vishay precision dividers in the
SOT-23 package which you might find interesting, if you need this sort
of ratio stability.

If you could be more specific about the precison and stability you
need, we might be able to come up with more specific information.

Bill Sloman, Nijmegen

Let's just forget this whole thing. Its easier to go out and buy 10-20 and measure
them.

SioL
Click to expand...
The inexpensive arrays don't match particularly well, from the few I
tested before getting bored, however the overall tolerance is pretty
good (similar range to the variation from unit-to-unit, IIRC).


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
There is one method that I used as a student to obtain resistors of very
high precision. The zero-budget method. But it is not at all suitable
for anything but non-critical hobby applications.

I took carbon resistors of a little lower value than I needed, the kind
that has a few turns. Then I sanded down until the lacquer layer was
partially gone. Now I changed to 600 grit paper and had at it until I
reached 12648.5 ohms or whatever. Now a little dab of fresh paint and I
had a "custom resistor". Don't know how long they held up but in the few
years I used them in a circuit they did well. BTW, I used to do the same
with quartz crystals to avoid having to shell out $10 or so for a custom
crystal. Lots more work though.

Regards, Joerg

http://www.analogconsultants.com
 
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:NDRuc.76939$LB6.64139@newssvr25.news.prodigy.com...
There is one method that I used as a student to obtain resistors of very
high precision. The zero-budget method. But it is not at all suitable
for anything but non-critical hobby applications.

I took carbon resistors of a little lower value than I needed, the kind
that has a few turns. Then I sanded down until the lacquer layer was
partially gone. Now I changed to 600 grit paper and had at it until I
reached 12648.5 ohms or whatever. Now a little dab of fresh paint and I
had a "custom resistor". Don't know how long they held up but in the few
years I used them in a circuit they did well. BTW, I used to do the same
with quartz crystals to avoid having to shell out $10 or so for a custom
crystal. Lots more work though.

Regards, Joerg
Click to expand...
wow, you are a glutton for punishment :)

I worked with a guy who used to tune crystals in a similar manner, using
pencil lead.

Cheers
Terry
 
"Bill Sloman" <bill.sloman@ieee.org> a écrit dans le message de
news:7c584d27.0405311349.49cff7d3@posting.google.com...
"SioL" <spam@spam.com> wrote in message
news:<yDHuc.4078$37.501863@news.siol.net>...
I've noticed 4 resistors are now available in a convenient SMD 1206
package.

Remember how transistors on the same die (like those transistor arrays)
used > to have closely matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.

Depends on which array you are talking about, and what sort of
matching you want.

Vishay can probably come up with +/-0.05% ratio tolerances and
+/-2ppm/C TCR tracking, if you go for the right parts.

I looked at something similar a few years ago, and could have got a
single tube of a more or less arbitrary set of values (the resistance
range couldn't exceed 10:1 within the array) for rather less than
$1000.

Farnell stock a restricted set of Vishay precision dividers in the
SOT-23 package which you might find interesting, if you need this sort
of ratio stability.
Click to expand...

Maxim now have some intersting devices too with their MAX5491 range.



Thanks,
Fred.
 
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:46Puc.62810$aw.29767@newssvr29.news.prodigy.com...
Can you post a URL with a datasheet?

Even the very small stuff I saw was all made on thick film and laser
trimmed. Done a lot of laser trim designs myself and since laser time is
$$$ you usually stop each trim location the millisecond you hit the
required tolerance. Any more trimming adds laser time and reduces
profit. Which means that in this scenario you cannot always guarantee
better tracking than the absolute tolerances are. Usually it is a bit
better than abs tolerance though because the laser always does the same
cut pattern. So if, for example, it would stop at plus 0.9% then the
resistors on that hybrid might all be within 0.1% or 0.2% of each other.
Might, no guarantees. Sometimes the cutting is coarse so the "steps"
between shots are just too much for good tracking.

Regards, Joerg
Click to expand...
Aha, I thought just perhaps they'd be using some kind of etching
process so they'd come out identical.

SioL
 
"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:vunnb0de0ru1omjog2f8k07igdoq619ee5@4ax.com...
On Tue, 1 Jun 2004 00:31:41 +0200, the renowned "SioL" <spam@spam.com
wrote:

Let's just forget this whole thing. Its easier to go out and buy 10-20 and measure
them.

SioL

The inexpensive arrays don't match particularly well, from the few I
tested before getting bored, however the overall tolerance is pretty
good (similar range to the variation from unit-to-unit, IIRC).


Best regards,
Spehro Pefhany
Click to expand...
That's what I was interested in, yes. Thanks.

SioL
 
"SioL" <spam@spam.com> wrote in message
news:MqOuc.4105$37.504993@news.siol.net...

Let's just forget this whole thing. Its easier to go out and buy 10-20 and
measure
them.
Click to expand...
Nah - Because you may well be screwed there also:

Some manufacturers get their "precision" resistors by selection from a batch
of "nominal" resistors - which means that the ones you buy on-the-cheap as
f.ex. 5% devices, in the hope of screening some exact values out, will have
a hole in the distribution around the nominal value i.e. the ones that are
selling as "precision" devices....

What to do then?

One could select the end of the distribution - but then the "yield" goes
down.

It is probably easier to use parallel resistors and make up the required
value by selection - if one must have a spot-on resistance.
 
"SioL" <spam@spam.com> wrote in message
news:MqOuc.4105$37.504993@news.siol.net...
"Bill Sloman" <bill.sloman@ieee.org> wrote in message
"SioL" <spam@spam.com> wrote in message
news:<yDHuc.4078$37.501863@news.siol.net>...
I've noticed 4 resistors are now available in a convenient SMD 1206
package.

Remember how transistors on the same die (like those transistor
arrays) used > to have closely
matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.

Depends on which array you are talking about, and what sort of
matching you want.

Vishay can probably come up with +/-0.05% ratio tolerances and
+/-2ppm/C TCR tracking, if you go for the right parts.

I looked at something similar a few years ago, and could have got a
single tube of a more or less arbitrary set of values (the resistance
range couldn't exceed 10:1 within the array) for rather less than
$1000.

Farnell stock a restricted set of Vishay precision dividers in the
SOT-23 package which you might find interesting, if you need this sort
of ratio stability.

If you could be more specific about the precison and stability you
need, we might be able to come up with more specific information.

Bill Sloman, Nijmegen

Let's just forget this whole thing. Its easier to go out and buy 10-20 and
measure
them.
Click to expand...
You won't often get +/-2ppm/C ratio tracking that way.

Farnell also stock a limited range of Vishay's surface mount precision
resistors, +/-0.01% tolerance, less than 0.6ppm/C between 0C and 60C, but
they are twice the size of the SOT-23 package and cost about $10 each.

If you are less ambitious, look at Farnell's 0603 0.1% precision resistors -
though they only stock the E6 values - or the 0805 0.1% 10ppm/C range where
they stock all the E96 values from 51R1 to 147k and 150k. About $1.50 each
and a minimum order of five per value.

If you solder a few of these in close proximity on a printed circuit board
you'll get pretty good temperature tracking (unless you dissipate
significantly different amounts of power in individual resistors).

--------
Bill Sloman, Nijmegen
 
bill.sloman@ieee.org (Bill Sloman) writes:

"SioL" <spam@spam.com> wrote in message
news:<yDHuc.4078$37.501863@news.siol.net>... > I've noticed 4
resistors are now available in a convenient SMD 1206 package.

Remember how transistors on the same die (like those transistor
arrays) used > to have closely matched characteristics?

I wonder if this rule applies to these resistors as well.

Could be handy for certain applications.

Depends on which array you are talking about, and what sort of
matching you want.

Vishay can probably come up with +/-0.05% ratio tolerances and
+/-2ppm/C TCR tracking, if you go for the right parts.
Click to expand...
I have wondered this myself.

I think he just means the cheaper types that are not normally
specified as precision components. It might be that although the
absolute tolerance is say +/- 5%, the relative matching of the 4
resistors might be much better than this, also the temperature
drift. Perhaps better than 4 individual 2% resistors.

You could then use one in e.g. the standard 3 op-amp differential
amplifier. Or any potential divider, perhaps using series-parallel
combinations of the elements.


--

John Devereux
 
On Tue, 1 Jun 2004 10:14:26 +0200, the renowned "SioL" <spam@spam.com>
wrote:

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:vunnb0de0ru1omjog2f8k07igdoq619ee5@4ax.com...
On Tue, 1 Jun 2004 00:31:41 +0200, the renowned "SioL" <spam@spam.com
wrote:

Let's just forget this whole thing. Its easier to go out and buy 10-20 and measure
them.

SioL

The inexpensive arrays don't match particularly well, from the few I
tested before getting bored, however the overall tolerance is pretty
good (similar range to the variation from unit-to-unit, IIRC).


Best regards,
Spehro Pefhany

That's what I was interested in, yes. Thanks.
Click to expand...
You're welcome. I think they are individually trimmed so they really
are no more accurate than individual resistors. OTOH, the tempcos
should track better because the material and temperatures are very
similar, but I think you'll find when you look at typical tempcos that
it's not such a big deal in most cases.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
"John Devereux" <jdREMOVE@THISdevereux.me.uk> wrote in message
news:upt8j37n9.fsf@plastech-controls.com...
I have wondered this myself.

I think he just means the cheaper types that are not normally
specified as precision components. It might be that although the
absolute tolerance is say +/- 5%, the relative matching of the 4
resistors might be much better than this, also the temperature
drift. Perhaps better than 4 individual 2% resistors.

You could then use one in e.g. the standard 3 op-amp differential
amplifier. Or any potential divider, perhaps using series-parallel
combinations of the elements.

John Devereux
Click to expand...
Yep, that's what I had in mind. Unfortunately it seems as if that's not
really viable (they're trimmed individually, not manufactured at the
same time).

They're cheaper than 4 individual resistors, though.

SioL
 
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