[time-nuts] GC-1000 Clock Cap Choice?

Dr. Frank Stellmach drfrank.stellmach at freenet.de
Sun Jan 16 23:08:18 UTC 2011


>I have found that such high dielectric constant capacitors have other
>  problems in some circuits.  While the capacitance value is dropping,
>  as much as 50% when you apply voltage, their physical volume is
>  changing.  They behave as piezoelectric transducers.

>  I have used them inappropriately, and found them singing loudly.  If
>  that were to happen in a switching regulator, I would think the ultrasonic
>  vibrations could do damage to the capacitor, the PCB, or the solder joints.

>  -Chuck Harris

We use ceramics widely in our applications, also switching power supplies and PWM circuits.

Our customers always search intensivley for audible and visual problems before accepting our products, (we design instrument clusters).

(X5R) ceranic capacitors did not yet pose any audible problems, but "singing" inductors did.
It is also known, that ceramics'* piezo effect is problematic for audio amplifiers.

I have to admit, that we do not use very high value caps; several µF is oK, higher values are either too expensive compared to ElCo and Ta, or too bulky.


Anyhow, if our dear customers require us to avoid Tantalums for safety concerns, Ceramics are looked upon first.

Frank






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