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From: TTman on 11 Oct 2009 10:50

"wzab" <wzab(a)ise.pw.edu.pl> wrote in message
news:slrnhd3rfr.tmi.wzab(a)wzab.nasz.dom...
> 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?
> --

The max 232 will give you 10 mA max..


From: wzab on 11 Oct 2009 11:51
On Oct 11, 4:50 pm, "TTman" <someone...(a)ntlworld.com> wrote:

>
> The max 232 will give you 10 mA max..

Thank you very much.
Now I have also found it in the "OUTPUT VOLTAGE vs. LOAD CURRENT"
chart on the 4th page
of the http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf
datasheet.
And in fact such use of MAX232 is accepted by the manufacturer.
However yet another question is the voltage quality.
I suppose, that the clock signal driving the charge pump will be also
present in the output voltage.
What is a typical frequency of this clock?
--
TIA & Regards,
WZab
From: Andrew Smallshaw on 8 Nov 2009 11:59
On 2009-11-07, boB <bob(a)bob.bob> wrote:
>
> I like the ST232A because its rails are
> a bit higher than other RS232 chips.

I like it because it is dirt cheap. Last time I needed fairly
small quantities of an RS232 driver the ST232 was 70-odd pence a
peice. The MAX232 was around four or five times that as I remember.
That's a big premium simply for the brand name genuine part.

--
Andrew Smallshaw
andrews(a)sdf.lonestar.org
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