I found a nice enclosure that I would like to use for a PIC based
product.  Unfortunalely this enclosure will only accept two AAA
sized penlight batteries, whereas many of the IC's in my prototipe
requires at least 5V.  I'm thinking of using two 1.2V Nicad
batteries.  Surely many other people on this list have also had a
requirement for something like this some time or other.

I know there are dc to dc converter and voltager doubler IC's
available from companies like Maxim, but I would still like to hear
the opinions of other list members about the usage of these types of
voltage doubler IC's.  Since there will also be a 5V, 12 bit A/D on
the circuit, I need something that is not very noisy and still quite
efficient.   I have never had to make such a battery operated
product before.  What would you recommend or not recommend?  Is it
feasible to run a 5V based circuit from a 20 - 2.4V  supply with dc
to dc conversion, or is it not recommended?

Rgds
Werner