NPO ceramic vs polypropylene

[George Herold]

NPO ceramic vs polypropylene

There was a little side discussion on JL’s LC tuning thread. When I looked at this ~2 years ago I found that ceramics were a tad better than the ‘good’ poly-pro’s.
(I used them in a low freq LCR circuit.. Q~35 so the cap type didn’t makethat much of a difference.)
(The poly pro’s I have are from Panasonic. low dissipation 2% caps. I can dig up a part number if it’s important, I’m not sure they are made anymore.)
So these are both 10nF caps. I first measured them on an SRS720. at 10 and100kHz.

10kHz 100kHz
type C R D R D
NPO 10.17 0.6 0.0004 0.006 0.00003
poly 10.16 0.23 0.00013 0.086 0.0056

The R/D numbers are so low I don’t really believe them.
So I stuck the C’s in the (original) LCR circuit. So I list peak frequency, Vin and Vout. (As measured on a ‘scope (digital w/average))

type freq. Vin Vout
NPO 6.08kHz 159mV 6.40V
poly 6.13kHz 159mV 6.36V

(again no real difference to talk about.) I pulled out a different L...

type freq. Vin Vout
NPO 157kHz 91.2mV 7.36V
poly 158.5kHz 92.8mV 7.24V

Finally a bit of difference I can believe. Vin dropped because the series LC was loading down the function gen.

So for those who think film are better, you might want to look again at NPOceramics. They've improved a lot*. Of course this says nothing about theDA of the caps. (How does one go about measuring that?)

George H.

*you need to get the new little ones.. the old larger npo ceramics with thedull brown coating are not nearly as good.

 

[[email protected]]

On Tuesday, November 19, 2013 11:52:20 AM UTC-5, George Herold wrote:

It's NP0 and not NPO, although that's the way it's pronounced. It is the numeral "oh."

 

[John Devereux]

On Tuesday, November 19, 2013 11:52:20 AM UTC-5, George Herold wrote:

It's NP0 and not NPO, although that's the way it's pronounced. It is the numeral "oh."

That's why they came up with COG, so we don't have to worry about that
anymore.

 

[Frank Miles]

NPO ceramic vs polypropylene

There was a little side discussion on JL’s LC tuning thread. When I
looked at this ~2 years ago I found that ceramics were a tad better than
the ‘good’ poly-pro’s. (I used them in a low freq LCR circuit.. Q~35 so
the cap type didn’t make that much of a difference.)
(The poly pro’s I have are from Panasonic. low dissipation 2% caps. I
can dig up a part number if it’s important, I’m not sure they are made
anymore.)
So these are both 10nF caps. I first measured them on an SRS720. at 10
and 100kHz.

10kHz 100kHz
type C R D R D NPO 10.17 0.6
0.0004 0.006 0.00003 poly 10.16 0.23 0.00013
0.086 0.0056

The R/D numbers are so low I don’t really believe them. So I stuck the
C’s in the (original) LCR circuit. So I list peak frequency, Vin and
Vout. (As measured on a ‘scope (digital w/average))

type freq. Vin Vout
NPO 6.08kHz 159mV 6.40V
poly 6.13kHz 159mV 6.36V

(again no real difference to talk about.) I pulled out a different L...

type freq. Vin Vout
NPO 157kHz 91.2mV 7.36V
poly 158.5kHz 92.8mV 7.24V

Finally a bit of difference I can believe. Vin dropped because the
series LC was loading down the function gen.

So for those who think film are better, you might want to look again at
NPO ceramics. They've improved a lot*. Of course this says nothing
about the DA of the caps. (How does one go about measuring that?)

George H.

*you need to get the new little ones.. the old larger npo ceramics with
the dull brown coating are not nearly as good.

Thanks, George, for an excellent response! I would be interested in the
part numbers but your numbers are certainly compelling for the NP0s. If
nothing else to make sure that we're not comparing a new-generation NP0 with
an older-generation metalized polypropylene. I've used the Panasonic ECW
series parts- the current web info is a bit confusing (a "built-in fuse
function" (deliberately added resistance?); not requiring "a significant
amount of pulse current" yet suitable for "high current circuits" ?.

An application that can make DA really stand out is with a sample-hold. For
example, charge a capacitor to some voltage and keep it there for some time;
then "short to ground" for a much shorter interval. Release the "short" and
watch the capacitor voltage (presumably with some extremely-low-bias-current
follower). In my tests (done a long time ago now - data long gone) the
met-polypros were the best of the lot for DA.

 

[George Herold]

Thanks, George, for an excellent response! I would be interested in the

part numbers but your numbers are certainly compelling for the NP0s. If

nothing else to make sure that we're not comparing a new-generation NP0 with

an older-generation metalized polypropylene. I've used the Panasonic ECW

series parts- the current web info is a bit confusing (a "built-in fuse

function" (deliberately added resistance?); not requiring "a significant

amount of pulse current" yet suitable for "high current circuits" ?.



An application that can make DA really stand out is with a sample-hold. For

example, charge a capacitor to some voltage and keep it there for some time;

then "short to ground" for a much shorter interval. Release the "short" and

watch the capacitor voltage (presumably with some extremely-low-bias-current

follower). In my tests (done a long time ago now - data long gone) the

met-polypros were the best of the lot for DA.

Yeah sure.. I hope digikey part numbers are OK.

poly was P3103-ND (ECQ series now discontinued.)
and ceramic 445-4750-ND
I think that was just the cheapest on the DK site... also lots of stock which is always a good sign.

I haven't looked at any others. We've got a few products with a high Q section somewhere in the signal chain and as the polypro's go away I've been replacing with ceramics.

I kinda wonder when ceramics became so good. Was there a breakthrough, or just incremental improvement?

George H.

 

[Tim Williams]

I kinda wonder when ceramics became so good. Was there a breakthrough,
or just incremental improvement?

C0G has always been C0G (except when it was called NP0, but you know..).
It's basically straight... titanium dioxide, or strontium titanate or
something? I forget. Once it was discovered, the material properties
remain constant, there's just variations in formulation and manufacturing
process. Most notably the multilayer process.

In my junk box, I have some monster NP0s from '60s TV sets. 100pF is a
one inch disc! Purity and, more importantly, density probably weren't so
great back then, so they had to use excess thickness to guarantee
dielectric strength (they might actually handle 5kV.. who knows?).

MLCCs must be using high density formulations, or finer grained material,
or something, which allows them to make micron thick layers. Then they
just make a lot of layers. Then they make a lot of caps. Millions of
caps. Billions. High speed production does its thing, the market
responds, and prices get where they are now.

Tim

 

[Tim Williams]

I _think_ that the dissipation angle is the arctan of the resistance
divided by the reactive impedance (or the arcsine of resistance divided
by the total impedance -- your choice).

So it's pretty much just another way of expressing Q -- or maybe it's a
convenient way of telling if the cap will roast, I dunno.

For DF << 1, Q ~= 1/DF. And angle follows from, say, the small angle
approximation, as long as you like radians.

You can, of course, express it as ESR or EPR, however you prefer; the
result is of course Xc divided by, or times, the Q, respectively.

It gets trickier in definition and measurement when DF is large (say >
0.1), but that only matters to polarized caps (and analogously, powdered
iron core chokes).

Tim

 

[JM]

I _think_ that the dissipation angle is the arctan of the resistance
divided by the reactive impedance (or the arcsine of resistance divided
by the total impedance -- your choice).

So it's pretty much just another way of expressing Q -- or maybe it's a
convenient way of telling if the cap will roast, I dunno.

I think he's talking about dielectric absorption when he mentions DA?

 

[Joerg]

Is that Charlie Oscar Golf, or Charlie Zero Golf?

In RF slang it's "cog", southern RF slang "caoag".

 

[Joerg]

NPO ceramic vs polypropylene

There was a little side discussion on JL’s LC tuning thread. When I
looked at this ~2 years ago I found that ceramics were a tad better
than the ‘good’ poly-pro’s. (I used them in a low freq LCR circuit..
Q~35 so the cap type didn’t make that much of a difference.) (The
poly pro’s I have are from Panasonic. low dissipation 2% caps. I
can dig up a part number if it’s important, I’m not sure they are
made anymore.) So these are both 10nF caps. I first measured them on
an SRS720. at 10 and 100kHz.

10kHz 100kHz type C R D
R D NPO 10.17 0.6 0.0004 0.006 0.00003
poly 10.16 0.23 0.00013 0.086 0.0056

The R/D numbers are so low I don’t really believe them. So I stuck
the C’s in the (original) LCR circuit. So I list peak frequency, Vin
and Vout. (As measured on a ‘scope (digital w/average))

Are you sure about the numbers? Where did you get the material or caps
from? My experience is more along the lines of these numbers:

http://www.conradhoffman.com/cap_losses.htm

Interestingly, we just had a discussion about this very stuff in a
meeting this morning. C0G is good, but it isn't quite this good. I had
my comeuppance in that respect as a teenager. I had completed a 1.2kW RF
amp for my ham radio station (before anyone bristles, that was legal in
Germany back then). For operation on 14MHz I was short one capacitor.
Found a nice big ceramic RF cap with low tempco, which must have been
C0G. Tuned it up, cranked up the power to the hilt ... *KABLAMMO* ...
and cap was gone. Literally, except for the wires. I found a few bits
and pieces and they had turned from white ceramic into bubbly green
glass. So the loss tangent must have been not too great.

type freq. Vin Vout NPO 6.08kHz 159mV 6.40V poly
6.13kHz 159mV 6.36V

(again no real difference to talk about.) I pulled out a different
L...

type freq. Vin Vout NPO 157kHz 91.2mV 7.36V
poly 158.5kHz 92.8mV 7.24V

Finally a bit of difference I can believe. Vin dropped because the
series LC was loading down the function gen.

So for those who think film are better, you might want to look again
at NPO ceramics. They've improved a lot*. Of course this says
nothing about the DA of the caps. (How does one go about measuring
that?)

George H.

*you need to get the new little ones.. the old larger npo ceramics
with the dull brown coating are not nearly as good.

What new little ones?

 

[Spehro Pefhany]

Thanks, George, for an excellent response! I would be interested in the
part numbers but your numbers are certainly compelling for the NP0s. If
nothing else to make sure that we're not comparing a new-generation NP0 with
an older-generation metalized polypropylene. I've used the Panasonic ECW
series parts- the current web info is a bit confusing (a "built-in fuse
function" (deliberately added resistance?); not requiring "a significant
amount of pulse current" yet suitable for "high current circuits" ?.

An application that can make DA really stand out is with a sample-hold. For
example, charge a capacitor to some voltage and keep it there for some time;
then "short to ground" for a much shorter interval. Release the "short" and
watch the capacitor voltage (presumably with some extremely-low-bias-current
follower). In my tests (done a long time ago now - data long gone) the
met-polypros were the best of the lot for DA.

PS film is better than PP film or C0G ceramics for DA, but they're not
very common.

--sp

 

[George Herold]

I _think_ that the dissipation angle is the arctan of the resistance
divided by the reactive impedance (or the arcsine of resistance divided
by the total impedance -- your choice).

So it's pretty much just another way of expressing Q -- or maybe it's a
convenient way of telling if the cap will roast, I dunno.

Yeah I think about it as 1/Q (there may be a factor of two in there.. no never mind I'm confusing it with the damping factor.) Anyway looking at thenumbers that are spit out by the srs lcr meter the dissipation factor is 'kinda' independent of the frequency. While what they call R depends on thefrequency. Which is pretty weird if you ask me. I'd expect the resistance to be roughly constant... Dang am I actually going ot have to read the manual?

OK D is 1/Q and R is the ESR. For the cermaic cap ESR (in ohms) (as measured by srs) is 2.3(1kHz) 0.65(10kHz) and 0.02(100kHz) Whereas D = 0.0001(1kHz), 0.0004(10kHz), 0.0001(100kHz) OK as you said D is the ratio of the impedances. So now the question is....
Why does the ESR change with frequency? Where does it come from?

Hey I did find that the srs720 has a set of optional tweezers!

George H.

 

[George Herold]

Are you sure about the numbers? Where did you get the material or caps
from? My experience is more along the lines of these numbers:

Grin.. well that's what the srs meter spat out. Roughly confirmed by a LC Q measurment, (but I'd really need a better big low loss inductor.... oh I could dig one out..)

http://www.conradhoffman.com/cap_losses.htm

Hmm well these TDK ceramics look better than that. They don't quote a DF spec though.

Interestingly, we just had a discussion about this very stuff in a
meeting this morning. C0G is good, but it isn't quite this good. I had
my comeuppance in that respect as a teenager. I had completed a 1.2kW RF
amp for my ham radio station (before anyone bristles, that was legal in
Germany back then). For operation on 14MHz I was short one capacitor.
Found a nice big ceramic RF cap with low tempco, which must have been
C0G. Tuned it up, cranked up the power to the hilt ... *KABLAMMO* ...
and cap was gone. Literally, except for the wires. I found a few bits
and pieces and they had turned from white ceramic into bubbly green
glass. So the loss tangent must have been not too great.

What new little ones?

Well the new multilayer guys versus the old bulky brown ones.
(I sent cass a digikey number.)
I noticed that TDK also list some high Q smd varieties.. they might have a quoted spec. I didn't check.

George H.

 

[Frank Miles]

PS film is better than PP film or C0G ceramics for DA, but they're not
very common.

--sp

Ah, you mean polystyrene? They are good, but their low melting point makes
them a non-starter in almost all circumstances.

 

[Frank Miles]

Are you sure about the numbers? Where did you get the material or caps
from? My experience is more along the lines of these numbers:

http://www.conradhoffman.com/cap_losses.htm

Interestingly, we just had a discussion about this very stuff in a
meeting this morning. C0G is good, but it isn't quite this good. I had
my comeuppance in that respect as a teenager. I had completed a 1.2kW RF
amp for my ham radio station (before anyone bristles, that was legal in
Germany back then). For operation on 14MHz I was short one capacitor.
Found a nice big ceramic RF cap with low tempco, which must have been
C0G. Tuned it up, cranked up the power to the hilt ... *KABLAMMO* ...
and cap was gone. Literally, except for the wires. I found a few bits
and pieces and they had turned from white ceramic into bubbly green
glass. So the loss tangent must have been not too great.

[snip]

Nice chart! This is also closer to my (old) measurements, including the mica
having unexpectedly horrible DA.

 

[Frank Miles]

George Herold wrote:



YUP, no kidding! I have been making servo amps for about 10 years, and
used PP film caps in the output filters. Had some problems with them
getting hot when the amp was run near 50% duty cycle for a while. I
originally tried to find affordable ceramic caps and couldn't find
anything less than several $ each. Now, I re-engineered it to use
ceramic NPO SMT caps that are about $0.35 each, and they run completely
cold under the same condition. That condition is 100 V approximately
sine wave at 50 KHz. So, I have changed both the output filter caps and
the snubber caps to NPO ceramic. The film caps couldn't stand the IR
reflow, so they used to be hand-soldered later. So, I have eliminated
several manual processes as a bonus.

Jon

In the amps you shipped me you were using polyesters.

 

[George Herold]

<snip>

OK D is 1/Q and R is the ESR. For the cermaic cap ESR (in ohms) (as measured by srs) is 2.3(1kHz) 0.65(10kHz) and 0.02(100kHz) Whereas D = 0.0001(1kHz), 0.0004(10kHz), 0.0001(100kHz) OK as you said D is the ratio of the impedances. So now the question is....

Why does the ESR change with frequency? Where does it come from?

So what's the source of the dissipation factor.
If wiki is to be believed,
http://en.wikipedia.org/wiki/Dissipation_factor
Then there are two sources of loss. Conduction electron loss or dipole relaxation.
And wiki finds the DF from conduction loss should go as 1/f. (f = frequency)

Which is not what I saw. (DF looks kinda constant for the ceramics.)
And this is a nice link for film caps,
http://www.alliedelec.com/images/Products/mkt/pb/cornelldubilier/pdfs/filmcapacitorsappguide.pdf

Which I would describe as
~constant DF for Polyester. (above 10kHz)
DF increases as ~f for Polyprop. (above 10kHz)
and PPS may also increase as ~f, but it's hard to tell because
of the linear-log graph. (people doing spec sheets should know how to graph.)

None of which fits the wiki model?

George H.

 

[[email protected]]

[email protected] writes:






That's why they came up with COG, so we don't have to worry about that

anymore.





--



John Devereux

That's a 0 (zero) too, for C0G and not COG. This derives from EIA RS-198. The letter C means significant digit of tempco in ppm/oK is 0.0, the second code is always numeric is multiplier for tempco designated by first code and 0 means x1, the third G means tolerance of tempco in the ppm/oK with G designating +/-30.

http://en.wikipedia.org/wiki/EIA_Class_1_dielectric#Class_1_ceramic_capacitors

 

[John Devereux]

That's a 0 (zero) too, for C0G and not COG. This derives from EIA
RS-198. The letter C means significant digit of tempco in ppm/oK is
0.0, the second code is always numeric is multiplier for tempco
designated by first code and 0 means x1, the third G means tolerance
of tempco in the ppm/oK with G designating +/-30.

http://en.wikipedia.org/wiki/EIA_Class_1_dielectric#Class_1_ceramic_capacitors

Ha ha, should have looked it up. So there is no escape. (I think my
brain was mixing it up with COG as in chip-on-glass LCDs).

 

[Baron]

Hi guys,

Spehro Pefhany Inscribed thus:

PS film is better than PP film or C0G ceramics for DA, but they're not
very common.

--sp

How do glass capacitors fare in relation ?
Thanks: