> Generally, tantalums are most *un* suitable for power supply 
> applications.
> They are quite prone to failure, sometimes in spectacular fashion. A
> low-Z aluminum is a much safer bet.
>
> If you *must* use them, then heavily derate the voltage (use a 
> capacitor
> rated for 3 times as high as the working voltage), and follow all 
> data
> book recommendations to the letter.

Yes. This is a warning which must be noted. Tantalum capacitors are 
superb when they work. They offer very high capacitance per size and 
excellent ESR. But in an amateur or experimental situation where 
conditions are not well behaved or well known they can fail 
catastrophically.

A tantalum cap that experiences a voltage spike higher than its rated 
voltage, even a very brief one, will often fail very spectacularly. 
They often smell bad, make interesting sounds, smoke, catch fire or 
explode in various combinations. I've seen  one do all of these in 
that order :-).

Manufacturers spec sheets often specify minimum supply impedances they 
should be used with and even suggest adding some ohms of resistance in 
series.

A **solid** aluminium capacitor has the advantages of tantalum without 
the catastrophic failure mode.



            Russell McMahon 

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