W
Winfield Hill
Guest
George Herold wrote...
Hey, that's a 1959 paper. Sure it's of any use now?
--
Thanks,
- Win
Hey, that's a 1959 paper. Sure it's of any use now?
--
Thanks,
- Win
G
George Herold
Guest
On Wednesday, May 1, 2019 at 11:37:51 AM UTC-4, Phil Hobbs wrote:
how to do a tunable filter with V-caps. (I need two of them
in series.) But what would an opamp V-cap para-amp look like? ...
You might be able to sell that just for the fun of the idea.
Heck I would like to build one even if I can't sell it.
(I found lotsa stuff behind paywalls
https://ieeexplore.ieee.org/document/1472516
George H.
So Phil, my para-amp comment was a lark. I've got some ideaOn 5/1/19 10:22 AM, George Herold wrote:
On Wednesday, May 1, 2019 at 8:58:49 AM UTC-4, Bill Beaty wrote:
No need for VC tuning diodes, we have VC variable ceramic capacitors.
Use any large-value ceramic capacitor. Measure the uF while applying a DC
bias, and watch what happens.
I tried this on a 22uF 10V cap, in 0805 package. At 2.6V, capacitance
decreased from 21uF to 10uF! At the rated 10V, capacitance was 2.55uF.
WTF
The suppliers have apparently been concealing the fact that, for very small
ceramics with large values, the capacitance value is not stable, and across
the voltage rating, can decrease by a factor of at least ten! (I only
measured one example. I bet there are others which behave even worse.)
Try finding this fact in a typical spec sheet. Your 10V capacitor might have
an advertised 5% tolerance, but only if you never actually apply 10VDC to it.
As Win says this has been known about this for a while.
'Your mission Mr Phelps(Beaty), should you choose to accept it, is
to turn this cap into a voltage tunable filter.'
or maybe a parametric amplifier ?
George H.
The problems are the tolerance and tempco. I have a reel of 22 nF Y5V
caps that are pretty good varactors. I've been meaning to try making a
paramp out of some, to see how good a LF noise figure I could get.
That would be a super amusing product.
how to do a tunable filter with V-caps. (I need two of them
in series.) But what would an opamp V-cap para-amp look like? ...
You might be able to sell that just for the fun of the idea.
Heck I would like to build one even if I can't sell it.
(I found lotsa stuff behind paywalls
https://ieeexplore.ieee.org/document/1472516
George H.
W
whit3rd
Guest
On Wednesday, May 1, 2019 at 4:24:22 PM UTC-7, George Herold wrote:
It'd look like the old Analog Devices 310 and 311, one supposes.
<https://archive.org/details/AnalogDevicesDataAcquisitionProductsCatalog1979/page/n97>
It'd look like the old Analog Devices 310 and 311, one supposes.
<https://archive.org/details/AnalogDevicesDataAcquisitionProductsCatalog1979/page/n97>
Guest
On Wednesday, May 1, 2019 at 9:16:56 AM UTC-4, Winfield Hill wrote:
While you can find data published on the voltage dependency of ceramic caps, this info is not always published by any given manufacturer. Then while some put this in their data sheets, others publish is on their web site in special documents separately. I kinda figure everything important will be in the data sheet, but obviously that is not the case.
The voltage dependency not only varies with the ceramic type, it varies with the voltage rating, with some having significant impact on the capacitance at different percentages of the rated voltage. Of course, this entirely depends on manufacturer as well. I suspect there is an element of the moon phase, season and election year as well. That's why they only publish "typical" curves and never max/min specs that I've seen. So caveat emptor.
--
Rick C.
- Get a 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
While you can find data published on the voltage dependency of ceramic caps, this info is not always published by any given manufacturer. Then while some put this in their data sheets, others publish is on their web site in special documents separately. I kinda figure everything important will be in the data sheet, but obviously that is not the case.
The voltage dependency not only varies with the ceramic type, it varies with the voltage rating, with some having significant impact on the capacitance at different percentages of the rated voltage. Of course, this entirely depends on manufacturer as well. I suspect there is an element of the moon phase, season and election year as well. That's why they only publish "typical" curves and never max/min specs that I've seen. So caveat emptor.
--
Rick C.
- Get a 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
C
Chris Jones
Guest
On 02/05/2019 03:45, Tim Williams wrote:
You could put a power resistor next to the capacitor on the PCB, and
re-anneal the capacitor from time to time!
You could put a power resistor next to the capacitor on the PCB, and
re-anneal the capacitor from time to time!
B
Bill Beaty
Guest
On Wednesday, May 1, 2019 at 7:22:33 AM UTC-7, George Herold wrote:
> or maybe a parametric amplifier ?
Or parametric *oscillator*? Nope, the response is far too
symmetrical, +- wise.
Ah, from your IEEE link it appears that this resembles the "half-
frequency soliton effect." Whack your wineglass, and the Faraday
surface waves on the wine will be at half the frequency of the
moving glass "piston." Or, listen during a dental cleaning, and
the ultrasound signal will become audible, as similar nonlinear-
ities create 1/2 F and 1/4 F harmonics rather than higher har-
monics.
Or, pump a swinging pendulum by pulling upwards on the string
(yanking twice per cycle, so your 2F drive will amplify the 1F
pendulum frequency.)
Huh, thinking on *rubbing* wet wine glasses ...I wonder if adding
a diode could create an oscillator, if it was part of a tank
circuit using the right value of 0603 ceramic cap? Where diode
losses were smaller than capacitor gain during every other
cycle? Must think more on this while less awake!
Other thing: these bad capacitors probably are exhibiting
ferroelectric saturation, analogous to ferromagnetic
saturation.
In that case the scandal is just like having some ferrite supply
filters rated for one amp, but finding that the inductance falls
by 10X when actually run at 1A! (And it only happens for the
physically smallest one-amp inductors, rather than all of them.
And the sellers never mention that your 1-amp rated filters must
never actually be run at more than 50mA!)
--
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty a chem washington edu UW Chem Dept, Bagley Hall RM74
billb a eskimo com Box 351700, Seattle, WA 98195-1700
ph X3-6195 http://staff.washington.edu/wbeaty/
> or maybe a parametric amplifier ?
Or parametric *oscillator*? Nope, the response is far too
symmetrical, +- wise.
Ah, from your IEEE link it appears that this resembles the "half-
frequency soliton effect." Whack your wineglass, and the Faraday
surface waves on the wine will be at half the frequency of the
moving glass "piston." Or, listen during a dental cleaning, and
the ultrasound signal will become audible, as similar nonlinear-
ities create 1/2 F and 1/4 F harmonics rather than higher har-
monics.
Or, pump a swinging pendulum by pulling upwards on the string
(yanking twice per cycle, so your 2F drive will amplify the 1F
pendulum frequency.)
Huh, thinking on *rubbing* wet wine glasses ...I wonder if adding
a diode could create an oscillator, if it was part of a tank
circuit using the right value of 0603 ceramic cap? Where diode
losses were smaller than capacitor gain during every other
cycle? Must think more on this while less awake!
Other thing: these bad capacitors probably are exhibiting
ferroelectric saturation, analogous to ferromagnetic
saturation.
In that case the scandal is just like having some ferrite supply
filters rated for one amp, but finding that the inductance falls
by 10X when actually run at 1A! (And it only happens for the
physically smallest one-amp inductors, rather than all of them.
And the sellers never mention that your 1-amp rated filters must
never actually be run at more than 50mA!)
--
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty a chem washington edu UW Chem Dept, Bagley Hall RM74
billb a eskimo com Box 351700, Seattle, WA 98195-1700
ph X3-6195 http://staff.washington.edu/wbeaty/
B
Bill Beaty
Guest
On Wednesday, May 1, 2019 at 4:24:22 PM UTC-7, George Herold wrote:
Oh, one more also: the bad capacitors show hysterisis. Maybe
a couple of percent, but I didn't measure it. After they've once
been exposed to full WVDC, their capacitance is less at zero volts.
And, if you reverse the polarity and slowly raise the voltage
again, first the capacitance INCREASES briefly, before dropping
as before! Very expected, since the previous "high" voltage had
semi-permanently "poled" the PZT ceramic, at least a bit.
Capacitors as permanent memory elements. Giant electrostatic
core-memory bits. But how did the capacitors start out without
an initial stored effect? Thermal annealing, as mentioned?
So, build a nonvolitile flip-flop using a bad capacitor as a
memory element, then either write a one or zero using pos and
neg pulses, or if no neg supply, instead use your hot resistor
to erased the stored poling. Stored "Electrification?" "Electri-
tization?"
If a reel full of bad capacitors are identical enough, then one
could build an array, add a lens, and take thermal image
snapshots.
Hmmm. If the year was ~1820, I could get everyone to describe
the dielectric poling process with the term "electri-fi-kating,"
and maybe that term would take off and become common. Your
capacitors stop working? Way too electri-ficated! (Analogous
to "magnetized." Or perhaps convince everyone to describe a
PM bar as having been "magnet-tificated.) Far too late to
have it work now though.
--
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty a chem washington edu UW Chem Dept, Bagley Hall RM74
billb a eskimo com Box 351700, Seattle, WA 98195-1700
ph X3-6195 http://staff.washington.edu/wbeaty/
Oh, one more also: the bad capacitors show hysterisis. Maybe
a couple of percent, but I didn't measure it. After they've once
been exposed to full WVDC, their capacitance is less at zero volts.
And, if you reverse the polarity and slowly raise the voltage
again, first the capacitance INCREASES briefly, before dropping
as before! Very expected, since the previous "high" voltage had
semi-permanently "poled" the PZT ceramic, at least a bit.
Capacitors as permanent memory elements. Giant electrostatic
core-memory bits. But how did the capacitors start out without
an initial stored effect? Thermal annealing, as mentioned?
So, build a nonvolitile flip-flop using a bad capacitor as a
memory element, then either write a one or zero using pos and
neg pulses, or if no neg supply, instead use your hot resistor
to erased the stored poling. Stored "Electrification?" "Electri-
tization?"
If a reel full of bad capacitors are identical enough, then one
could build an array, add a lens, and take thermal image
snapshots.
Hmmm. If the year was ~1820, I could get everyone to describe
the dielectric poling process with the term "electri-fi-kating,"
and maybe that term would take off and become common. Your
capacitors stop working? Way too electri-ficated! (Analogous
to "magnetized." Or perhaps convince everyone to describe a
PM bar as having been "magnet-tificated.) Far too late to
have it work now though.
--
((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty a chem washington edu UW Chem Dept, Bagley Hall RM74
billb a eskimo com Box 351700, Seattle, WA 98195-1700
ph X3-6195 http://staff.washington.edu/wbeaty/
T
Tim Williams
Guest
"George Herold" <gherold@teachspin.com> wrote in message
news:db0d2a2f-ecb4-448d-b9f3-3a5595a3e40b@googlegroups.com...
>Bill that was very interesting, thanks.
(I would only use cog/npo ceramics in a filter.)
But it does go to show that ~energy storage goes as the volume.
(hmm, not sure that's true. Well at least that's ~true for film caps.
>
Energy density is proportional to k, so you can figure it out pretty easily
for type 2 dielectrics assuming a practical threshold for saturation (say
30%).
You can still keep going to higher voltages -- energy keeps going up, even
if not as quickly as you would've liked.
As it happens, saturation tends to follow a curve such that the energy is
approximately linear with voltage, after a curved toe-in (from the linear
range).
It turns out, the breakdown of type 2 dielectric is significantly worse,
too. So despite C0G being so much lower k, you can stack that many more,
thinner, layers before it breaks down, mostly recoup the value, and better
the energy density.
The real downside is, those layers are, I don't know, probably nanometers,
if you wanted say a "6.3V" cap. You can't make that with a ceramic tape
process. So, C0G is only economical for energy storage at high voltages,
over 200V or so. (Meanwhile, 100 and 250V X7Rs are just _atrocious_ in
C(V), so you need so much more than advertised, to get what you need.)
It may follow that, despite its fairly low k, diamond makes capacitors of
the highest energy density. I haven't looked at the properties though.
One very different thing you can do: polarize the dielectric, making an
electret. This shifts the voltage where the capacitance peak is placed.
And, because maximum capacitance is seen at real voltage, it absorbs massive
energy! (The ~2015 Google Little Box inverter contest winner used this as
the solution for energy storage to carry supply ripple.) Downside? Type 2
dielectrics anneal at soldering temperatures. So... you can either polarize
it in situ (during or after soldering) -- good luck with that; or, you very
carefully hand-solder a pre-polarized part.
They're also not cheap, but that's to be expected from niche components.
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
news:db0d2a2f-ecb4-448d-b9f3-3a5595a3e40b@googlegroups.com...
>Bill that was very interesting, thanks.
(I would only use cog/npo ceramics in a filter.)
But it does go to show that ~energy storage goes as the volume.
(hmm, not sure that's true. Well at least that's ~true for film caps.
>
Energy density is proportional to k, so you can figure it out pretty easily
for type 2 dielectrics assuming a practical threshold for saturation (say
30%).
You can still keep going to higher voltages -- energy keeps going up, even
if not as quickly as you would've liked.
As it happens, saturation tends to follow a curve such that the energy is
approximately linear with voltage, after a curved toe-in (from the linear
range).
It turns out, the breakdown of type 2 dielectric is significantly worse,
too. So despite C0G being so much lower k, you can stack that many more,
thinner, layers before it breaks down, mostly recoup the value, and better
the energy density.
The real downside is, those layers are, I don't know, probably nanometers,
if you wanted say a "6.3V" cap. You can't make that with a ceramic tape
process. So, C0G is only economical for energy storage at high voltages,
over 200V or so. (Meanwhile, 100 and 250V X7Rs are just _atrocious_ in
C(V), so you need so much more than advertised, to get what you need.)
It may follow that, despite its fairly low k, diamond makes capacitors of
the highest energy density. I haven't looked at the properties though.
One very different thing you can do: polarize the dielectric, making an
electret. This shifts the voltage where the capacitance peak is placed.
And, because maximum capacitance is seen at real voltage, it absorbs massive
energy! (The ~2015 Google Little Box inverter contest winner used this as
the solution for energy storage to carry supply ripple.) Downside? Type 2
dielectrics anneal at soldering temperatures. So... you can either polarize
it in situ (during or after soldering) -- good luck with that; or, you very
carefully hand-solder a pre-polarized part.
They're also not cheap, but that's to be expected from niche components.
Tim
--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
G
George Herold
Guest
On Wednesday, May 1, 2019 at 9:43:32 PM UTC-4, Bill Beaty wrote:
Right, pumping a swing by standing on it and going at
twice the freq. can be dangerous.
So maybe a parametric oscillator first.
Something like this?
+-----------+--- Vout
| |
V_bias.DC---R_b---+ ___ )
| ___ C1 )L1
| | | | )
+-----| |----+-----+ |
V_in.AC | | | |
___ |
both input ___ C1 |
Voltage sources | |
tied to Gnd +-----------+
not shown |
Gnd
Where C1's are big voltage coef caps.
I want small high voltage caps for a big voltage coef,
digikey..
George H.
Right, pumping a swing by standing on it and going at
twice the freq. can be dangerous.
So maybe a parametric oscillator first.
Something like this?
+-----------+--- Vout
| |
V_bias.DC---R_b---+ ___ )
| ___ C1 )L1
| | | | )
+-----| |----+-----+ |
V_in.AC | | | |
___ |
both input ___ C1 |
Voltage sources | |
tied to Gnd +-----------+
not shown |
Gnd
Where C1's are big voltage coef caps.
I want small high voltage caps for a big voltage coef,
digikey..
George H.
G
George Herold
Guest
On Thursday, May 2, 2019 at 2:48:05 AM UTC-4, Tim Williams wrote:
Yeah I don't know much about the k coef. I am replacing all
film caps up to about 0.1 uF with cog ceramics, cheaper and
better, mostly.
George H.
Yeah I don't know much about the k coef. I am replacing all
film caps up to about 0.1 uF with cog ceramics, cheaper and
better, mostly.
George H.