Good Queston #2: EG cap

[patchell]

    I would say not because I would use niether.  First off, the
tolerence on the capacitance is not very good on aluminum electrolytics.
In the applications that they are used on, being close is good enough.
You will often see +80 -20 % tolerences on aluminum elects.  Tantalums
are not much better, although typically you see +/- 10 or 20% on those.
Still, as far as being capacitors, they are far from ideal.  They have
awful problems with memory (dialectric absorbtion or what ever) among
others.  If you wish to make good timing circuits, stick with Polyester
for so-so and Polystyrene for very good.  If you can't get a capacitor
the size you need, scale the impeadence of the timing circuit.  Using
OTA's for the "resistive" element, I generally find that I never need to
go above .1uF to get agonizingly long time constants.  Just MHO.

    -Jim

KA4HJH wrote:

> Is there any practical advantage to using a tantalum cap instead of
> aluminum electrolytic as the timing cap in a slewing circuit such an
> envelope generator?
>
> What if you need fairly precise and repeatable control of the timing,
> e.g., an analog EG under digital control?
>
> Terry Bowman, KA4HJH
> "The Mac Doctor"
>
> ICQ: 45652354

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