[Hallicrafters] Piezo

[Peter Bertini]

Clifton Labs did a very nice presentation on the limits of
ceramic disk caps for *some *applications:

http://www.cliftonlaboratories.com/capacitor_voltage_change.htm

Note the charts that show capacitance change vs. applied voltage. That's why
I would avoid using them in audio coupling applications. He also provided
some harmonic distortion measurements.

His data for NPO and C0G disks vs. dipped micas also surprised me.

I'd still stand by their effectiveness for low impedance bypassing.

Pete

On Sun, Jan 2, 2011 at 12:13 PM, Wilson Lamb <infomet at embarqmail.com> wrote:

> I expect the material in disc caps is similar to that in piezoelectric
> transducers.
> Bias is not required to generate signals.  Just put a .01 disc on a scope
> and tap it.  I haven't, but you may well see a little spike.
>
> I think the microphonics are "reduced" when signals are strong because you
> can't hear them.  The presence of audio would not generally affect the
> generation of the piezo signal.
>
> 73,
> Wilson
> W4BOH
>
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