Linear Tech just introduced a new negative side regulator, the LT3015 -- now the positive regulators have a mate.
There's an interesting commentary on the bias non-linearity of certain ceramic capacitors in the LT3015 datasheet, plus a graph which had to have been done by the late Jim Williams on the piezo-electric effect of tapping a device with a ceramic cap.
There's an interesting commentary on the bias non-linearity of certain ceramic capacitors in the LT3015 datasheet, plus a graph which had to have been done by the late Jim Williams on the piezo-electric effect of tapping a device with a ceramic cap.
Why would one use a ceramic cap to vibrate a device?
I would find a little toffee hammer, it's sure to do a better job of finding resonances !
Ceramic caps do not remain "linear" when pulsed with varying voltage.
This applies to Low and Medium and High K versions. It seems the regularly recommended C0G and NP0 behave similarly when voltage varies.
When ceramics are used in decoupling duty, where voltage is held substantially constant, the ceramics have few peers.
Now to go and find that LT note and learn some more.
I would find a little toffee hammer, it's sure to do a better job of finding resonances !
Ceramic caps do not remain "linear" when pulsed with varying voltage.
This applies to Low and Medium and High K versions. It seems the regularly recommended C0G and NP0 behave similarly when voltage varies.
When ceramics are used in decoupling duty, where voltage is held substantially constant, the ceramics have few peers.
Now to go and find that LT note and learn some more.
nonlinear PS cap? - so what?
title misleading, Andrew's post just compounds the error of lumping "Ceramic" caps together
np0/c0g are better than some plastic film caps on all measures - they are not piezoelectric, have negligible Vcoeff - distortions can be measured but can be as low as -100 dB level
for power reservoir/bypass there are highly piezoelectric ceramic formulations - high K ceramics are not suitable for signal path use
whether their application in PS has a problem with piezo electric or nonlinear Vcoeff of high K dielectric ceramic caps is dependent on the circuit
the "non ideal" properties of the high K parts are a trade off for size, which reduces parasitic inductance - critical for sw mode supply bypass
so what is the point of the thread - what about nonlinear caps in PS?
title misleading, Andrew's post just compounds the error of lumping "Ceramic" caps together
np0/c0g are better than some plastic film caps on all measures - they are not piezoelectric, have negligible Vcoeff - distortions can be measured but can be as low as -100 dB level
for power reservoir/bypass there are highly piezoelectric ceramic formulations - high K ceramics are not suitable for signal path use
whether their application in PS has a problem with piezo electric or nonlinear Vcoeff of high K dielectric ceramic caps is dependent on the circuit
the "non ideal" properties of the high K parts are a trade off for size, which reduces parasitic inductance - critical for sw mode supply bypass
so what is the point of the thread - what about nonlinear caps in PS?
I can imagine an unimaginary scenario in which some badly behaving ceramics are beating to the tune of the vibrations in a CD/DVD/SACD player.
We need someone with an HP35670 or SR785 and a bunch of accelerometers to see how badly behaving ceramics are influenced by mechanical and musical vibration, and how they may affect the quality of reproduction.
We need someone with an HP35670 or SR785 and a bunch of accelerometers to see how badly behaving ceramics are influenced by mechanical and musical vibration, and how they may affect the quality of reproduction.
The solution is simple: use appropriate components for the application. In the digital part of the player a ceramic cap may be the best RF decoupler, provided that there is also audio decoupling to short out any piezo voltage. Glitches from supply or ground bounce could upset the audio far more than piezoelectricity.
I have seen DVD rotation frequency sidebands on a OPPO player's analog out with a single tone sine on test DVD I burned
common ground impedance coupling, inductive loop coupling are probably the 1st things to get right
decent PSRR in the analog circuit helps too
so far I haven't traced any problems to cap piezoelectric behavior in stain gage amps with gain up to 8000, 16 bit ADC, DSP, Ethernet or USB on one board with the analog front end
common ground impedance coupling, inductive loop coupling are probably the 1st things to get right
decent PSRR in the analog circuit helps too
so far I haven't traced any problems to cap piezoelectric behavior in stain gage amps with gain up to 8000, 16 bit ADC, DSP, Ethernet or USB on one board with the analog front end
Y5V capacitors should not be used at all. Their high cap/size ratio is more or less marketing scam. This got big attention in a couple of recent years, as soon as capacitor vendors started to publish Cap/Voltage plots. They will have ~5x smaller capacitance in real application, compared to part value.
X5R and X7R should be OK to decouple voltage rails for analog path. Peso effects would be hardly noticeable if they are used together with electrolytic caps. Vibrations should have big amplitudes at low frequencies, where el caps and voltage regulator feedback is capable of suppressing piezo effects in ceramic caps. Just necessary to have in mind that most of linear regulators will become unstable with big low ESR cap at the output. ESR value should be taken into account. ESR of more than 30 mOhm is usually OK for stability. And ceramic will provide good decoupling at relatively high frequency.
X5R and X7R should be OK to decouple voltage rails for analog path. Peso effects would be hardly noticeable if they are used together with electrolytic caps. Vibrations should have big amplitudes at low frequencies, where el caps and voltage regulator feedback is capable of suppressing piezo effects in ceramic caps. Just necessary to have in mind that most of linear regulators will become unstable with big low ESR cap at the output. ESR value should be taken into account. ESR of more than 30 mOhm is usually OK for stability. And ceramic will provide good decoupling at relatively high frequency.
Nah, you can just plug them into a guitar amp! Not quite as good a a real pickup but they do work!
not really, theres been lt1175 for quite some time and this, while marginally better, is still not the equal of the excellent 3A lt1764a or lt1963a, or even on the lower current low noise side, the 500ma lt1763. since the lt1033 is out of production (though still available around the place) there is only the lt317/337 that are really similar enough in dynamic performance to be used as a bipolar regulator and those that have been close have only been available in wildly different physical packages from each other.
at least its available in some of the same packages as the 1764a and 1963a. you are right though, the books at LT have been pretty badly weighted on the positive side, for lack of a compliment to the low noise ldos i ended up using the lt3032 bipolar reg chip and modifying the pcb pattern to allow it to be hand soldered.
still, all the same, imo they do not have any real competition in the IC regulator sector and the app notes and datasheets are so thorough its sublime
and relying on capacitor performance for regulator input ground? (unless you mean something different) yeah i realize and i considered that, but a lot of these regs (at least the best ones) have a ground pin (which complicates max Vout and/or the speed of the reg (or rather max Vin->Vout) and i'm utilizing sense and shdn pins on those and other regs on the board, so would have been more complicated than just using the bipolar chip. plus all the cuffuffle about Vground at the time kinda put me off that idea, diode drop wasnt part of the equation as this is a battery operated circuit.
Tapping a capacitor to observe some piezoelectric effect is hardly representative of audio use, try putting the same cap inside a speaker box isolated from the sides in a corner somewhere and observing the generated voltage at 80 or 90 dB spl as might be found inside an amplifier case. Then use the signal generated in the simulation (ac source in series with capacitor inserted at same location). Tapping can generate spl's of over 150 dB in the material.
The test suggested can easily be modified to simulate any board vibration and the board mounting can be optimised to minimise any sound pressure induced effects.
If the builder is keen put the finished amplifier inside a speaker box, short the input and observe what output signal if any appears with a frequency sweep.
The other components will also experience the same stresses, as will the solder joints etc, best to minimise board vibrations, not good for todays smaller packages especially now a lot of SMD components dont have compliant leads that will absorb some of the vibrataion. We use ceramics for decoupling (they are excellent for that purpose) but only X7, X8 or COG, we vibration test to DEF-STAN 00-35 Part 3, and a couple of other standards and have dont see any issues. We would not use them in directly in the audio path though (except for COG, but the values are of no use, COG are used in RF circuitry though were the values are benefitial. We also use COG for crytal oscillator decoupling because of their good RF properties.
I did my first experiments with SMPS in the 60th when i first was able to get a "fast" silicon power transistor. To keep losses down with the components I had at that time I had to operate them between 5 and maybe 12 khz. This was when I first heard real "capacitor sound". I was totally unable to find any type of capacitor that was silent enough to be useful without extensiv acoustic shielding. Without shielding the sound of almost any plastic encapsulated cap was totally unnerving.
Even the 2N3055 when driven hard could be clearly heard but much less annoying then the caps.
This expirience gave me the idea that this migth be a good test to nowdays capacitors for audio use.
Just run a decent amount of ac current through them and listen to your caps.
IF YOU USE THEM IN A RESONANCE CIRCUIT PLEASE, DONT OVERDUE IT!
PLEASE WATCH THE TEMPERATURE RISE BECAUSE SOME CAPS CAN SIMPLY MELT DOWN OR BLOW INTO YOUR FACE ! USE EYE PROTECTION!
If you have a amp that is able to deliver continiously the current needed
you could sweep over the audioband and listen.
You will find all kind of mechanical noises and resonances.
Always use a current limiting resistor in series with the cap.
Even the 2N3055 when driven hard could be clearly heard but much less annoying then the caps.
This expirience gave me the idea that this migth be a good test to nowdays capacitors for audio use.
Just run a decent amount of ac current through them and listen to your caps.
IF YOU USE THEM IN A RESONANCE CIRCUIT PLEASE, DONT OVERDUE IT!
PLEASE WATCH THE TEMPERATURE RISE BECAUSE SOME CAPS CAN SIMPLY MELT DOWN OR BLOW INTO YOUR FACE ! USE EYE PROTECTION!
If you have a amp that is able to deliver continiously the current needed
you could sweep over the audioband and listen.
You will find all kind of mechanical noises and resonances.
Always use a current limiting resistor in series with the cap.
I guess that you mean acoustic emission from the capacitor, some capacitors exhibit piezoelectric effect just as inductors can experience magnetostrictive effects. Good design can reduce this to minimal proportions for example some electron beam deflection devices have currents from 1kA to 8 kA with rise times in the millisecond to microsecond range and the better ones only make a small click when triggered.
I have some induction heating capacitors which make very little noise with 200 kVAR @ 10 kHz circulating in them.
These are fairly high powered applications, many audio capacitors only see microamps and microwatts so any test of them should reflect the intended use, The easiest test of all is to run the amplifier at full power into a dummy load and listen to it.
Yes metalsculptor, acoustic emission from the cap...
In a ceramic cap it sure is do to high-k ceramics piecoeffects.
High capacitance caps built for high power applications like induction heaters use normally multi layer structures with low k ceramics. The 200kVAr cap you mention would have a max voltage rating, a maximum current rating and a maximum power rating. Together with the capacitance we could define the best suitable frequency range.
As long as we use them within those ratings we could be sure that the manufacturer took care that possible electromechanical resonances dont occur inside of the intended
frequency range of operation. Anyway, with a mechanical heavy structure and often a outlay even for water cooling this wont be a problem.
But those caps arent exactly the same build as those used in DIY audio
equippement.
Fact remains, caps we use in audio equippement should be checked for possible sound emission.
And powersupply bypass caps either pass amps of current (if they are of any use),
or they simply dont (in wich case they are useless anyhow)
In a ceramic cap it sure is do to high-k ceramics piecoeffects.
High capacitance caps built for high power applications like induction heaters use normally multi layer structures with low k ceramics. The 200kVAr cap you mention would have a max voltage rating, a maximum current rating and a maximum power rating. Together with the capacitance we could define the best suitable frequency range.
As long as we use them within those ratings we could be sure that the manufacturer took care that possible electromechanical resonances dont occur inside of the intended
frequency range of operation. Anyway, with a mechanical heavy structure and often a outlay even for water cooling this wont be a problem.
But those caps arent exactly the same build as those used in DIY audio
equippement.
Fact remains, caps we use in audio equippement should be checked for possible sound emission.
And powersupply bypass caps either pass amps of current (if they are of any use),
or they simply dont (in wich case they are useless anyhow)
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