A 555 configured as a voltage inverter is cheap and works well; of course at 
lower current ratings.

----- Original Message ----- 
From: "Apptech" <apptech@paradise.net.nz>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Friday, May 02, 2008 10:15 PM
Subject: Re: [EE] CD4052 Question


>> Through the discussion I
>> confirmed I will need positive and negative supplies.
>
> Read my reply or replies again.
>
> You do NOT need dual supplies if you don't want to use them.
> What you do need to ensure is that the analog signal always
> residesd within the upper and lower DC rails that you do
> use. It is a simple matter to ensure this if that is
> prefereable to using dual supplies.
>
> A MAX232 or similar chip is an OK means of providing a
> negative supply. Filtering needs to suit the requirements of
> the application. There are many ICs that do this just as
> well or better with minimal parts. Even an MC34063 will do
> it with (apart from filter caps) one capacitor (oscillator)
> and 2 resistors (setting the voltage) and a 1N4148 or
> similar diode. This is a much more flexible solution for a
> singhle extra supply than a MAX232 fwiw.
> (Join pins 1,6,7,8. Ground pin 4. Osc cap pin 2 to ground.
> See app note for topology that suits for the rest).
>
>
>
>        Russell
>
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