Ceramic capacitor value changes drastically with DC bias

Here in CA, when sudden weird jitters start to appear on a circuit like that, it's better to get the hell out of the building :-)

Years ago when I used to do some repairs for my buddies, I had one bring me a guitar amplifier. He could not use it because it was feed back, even when nothing plugged into it. He also noted when tapping on the cabinet, it was perfectly microphonic.

When I finally found the problem, it was a transistor in a plastic package. The package was fine and so was the transistor but something inside broke loose and was playing with the beta and made a perfect microphone.

I used that transistor in an FM oscillator and it worked perfectly as a bug!..

Jamie

Grin... well can you turn the lemon into lemonade? some sort of vibration sensor... upthread tm said to heat it above it Curie temperature.

George H.

Grin... well can you turn the lemon into lemonade? some sort of vibration sensor... upthread tm said to heat it above it Curie temperature.

George H.

With a DC voltage applied. Allow it to cool with the DC applied and it should become very microphonic. Put an audio tone on it and you should hear it sing. Usually a soldering iron will get it hot enough but the material makes a difference.

e a

ar

Yeah I was going to ask what the curie temperature is? Is there a better 'flavor'?

Thanks, George H.

It's all about "podium"... the inadequate need it perpetually renewed. ...Jim Thompson

AFAIK, barium titanate and related blends are in the 120C+ range, maybe

If you have old discs that aren't measuring right, you can try soldering them, I suppose the mass and size of the disc may prevent the whole thing from heating up.

Tim

You're whining again. What do you have to say about capacitor dielectrics?

And what do you have to say about capacitors?

Sad old fool.

--- So, instead of admitting that your statement was self-serving and irrelevant, you dodge by pulling your one-trick pony out of the barn and have him whinny the "whine" word? How typically Larkinistic!

As for the dielectrics themselves, instead of wasting a lot of my time trying to reason with a hostile "client",

and

are good tutorials, with the latter illustrating the voltage coefficient of capacitance of the dielectric,

as does:

from within

However, the underlying cause of the parametric capacitance isn't gone into, and might be worth discussing if you can keep a civil tongue in your head.

Otherwise, f*ck off.

-- JF

So, when pushed into a corner, you can actually use google.

Hey, *that* was funny. Not creative, but funny.

You ought to know that Larkin _never_ puts forth anything that can be substantiated. ...Jim Thompson

What's actually going on here is that you have fallen so far behind the times, become so specialized, that you can understand only a small fraction of what's posted here. That's why you stay out of the more interesting threads, or only make lame posts about your Lexus and killing liberals and stuff.

Getting obsolete is a hazard of getting older. You've got to fight it.

Piezo elements are too expensive I presume? :-)

I use them in a design for detecting pressing a 'button' through metal. If that isn't sub-Hertz... and the signal is pretty decent. Maybe they work better if you stick them on a medium (plastic) which can be warped a bit by the sound pressure.

Take apart one of those piezo butane lighters and get a whole stack of them.