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Capacitor games...

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hjames

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I was just looking at some ceramic capacitor data sheets, and I wanted to see just how *bad* the Y5V capacitor material specs are:

https://www.electro-tech-online.com/custompdfs/2007/03/cy5v.pdf

Personally I avoid these for my designs, but I was thinking that some applications might be able to use these features - namely the horrible temperature and bias ratings:

~60% of the capacitance is lost by the time it reaches 60C over room temp
They're cheaper than thermistors, but are only usable over the room temperature range and above. They would definitely require a lot of care in the calibration process - but outfitting an entire board with an array of these would be really cheap, and would let you map out the temperature distribution in an interesting (but not obviously useful) way.

~80% of the capacitance is lost when the bias voltage reaches 40% of it's rating, and the transfer curve is very steep in the first 25%.
6.3V/10uF capacitors are US$0.2 or so, and will lose 7uF when the bias voltage reaches ~1.5V. That is a ludicrous amount of capacitance change. Mind you that it is only applicable for small signals, but imagine an adjustable capacitive attenuator or an isolated voltage sensor using a large Y5V sense cap and a pair of (good/C0G) bypass/isolation caps...

Has anyone seen anything that does anything creative with these parameters?
 
Voltage controlled oscillator?

I believe I saw a circuit like that awhile ago.
 
Has anyone seen anything that does anything creative with these parameters?
I think these are not actual "features" but the trade off from getting a large capacitance in a very small package. But it does give the twisted mind some evil ideas! ;)
 
It's called feedback =) It comes in all kinds of forms!
 
Hmm, I'm going to be away from a soldering station for a couple weeks (i.e. vacation), but I'm going to see if I can think up of some really bad ways of using this.

Off the top of my head:
Nonlinear integrator circuit - the gain scales by a factor of 5 while going through the scale
Use some zener diodes to shape the capacitance function in very unnatural ways - a really messed up variant of a typical waveform shaper.
stabilizing a sine wave oscillator.
I wonder if anything can come of using these in a typical bridge configuration.

Then there's the whole acoustic aspect to ceramic capacitors... Definitely unwholesome stuff
 
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