At 06:59 PM 5/14/2005 +0100, you wrote:
> > Use ceramics with decent dielectric characteristics (eg. X7R) and
> > sufficient voltage rating. They are small, cheap and reliable.
> > In some cases you may wish to use higher than  the 0.1uF (see curves).
>
>Are ceramics  also plarised like electrolitic,

No, they are not polarized like an electrolytic capacitor.

>can't I use just any
>old capacitor I can find?

If it's your parts, I suppose you can do whatever you like with them.
Just about any part with sufficient voltage rating and around the right
capacitance or more will probably be functional at room temperature.

Capacitance, voltage rating, temperature effects, ESR, lifetime, cost,
PCB real estate, and so on might enter into a rational design
consideration, however.

0603 0.1uF 25V X7R ceramic caps are a penny or less each and take up
precious little precious PCB real estate. If it's just an occasional-use
set-up port, then that's what I'd use. You can even get them with leads
if your technology level is set to "nostalgia". As Olin says you can get
1uF ceramics for reasonable prices with reasonable dielectrics these days,
but you'd probably want to give some thought to the optimum case size and the
proper voltage rating for each part(the latter varies with the place in the
MAX232 circuit, the way you decide to connect the caps, and with how
conservative you are).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
 >>>Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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