HI: as you say, you need a SIMPLE amplifier, so why you choice an amplifier which need +-8V power supply? because of your 5V battery, if you use an +-8V power multiplier(no matter by the one reffered by wiki or with 232chips), the battery life need to be caculated. And last, if the amplifier is unable to change, you can study the 232 chips to make sure how many 232 client the chip can drive(it is different between MAX232 or LTC232 or DC232 bra,bra...), by this way you can caculate the max current ability of +-12V power. About the RC filter, em... maybe a big cap is better. Only some idea, and you need to do experiment to verify. /Zona On Sun, 11 Oct 2009 15:29:09 +0200 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? > -- > TIA & Regards, > WZab > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- BR. ---- Zona -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist