As others have said, why not just use a 0 to 5V opamp.   I use a MCP6024 
in a lot of my circuits (2.5V to 5.5V power supply, rail to rail inputs 
and outputs). 

And, in case you are worried about measuring stuff outside of the 0 to 
5V range on the input, you can usually level shift with resistors on the 
front end of the OPAMP.

Lots cheaper than a +- power supply.

-forrest

wzab wrote:
> Hi,
>
> I need to add simple amplifier to my digital system which is powered 
> from a single 5V battery.
> To achieve proper operation of the operational amplifier I need at least
> +8V and -8V voltages.
> I can build a simple voltage multiplier and inverter like shown here:
> http://upload.wikimedia.org/wikipedia/en/thumb/b/ba/Stacked_Villard_cascade.svg/400px-Stacked_Villard_cascade.svg.png
> using the 6-CMOS inverter chip as an oscillator and a source of alternating
> voltage.
>
> However antoher idea is to use something cheap and standard like MAX232.
> Has anybody tried to use this chip just as a voltage converter?
> Unfortunately I can't find the output characteristics for V+ and V- pins.
> Maybe I'll need also additional voltage regulator to improve the quality of
> this power supply voltage (or maybe simple RC filter will be sufficient...).
>
> Has anybody tried to do it?
>   

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