Hello,

How can I power an opamp with polarized supply? I mean, how can I get the "V-"?
Can someone sugest me a circuit or IC?

Requirements
Input: 5V (or 3.3V)
Output: -5V (or -3.3V)
Small size

Thanks in advance!

 

You would need some sort of switching converter for that, they are available as monolythic circuits CPC stock them, as would many other supplyers I am sure.
(Asuming you dont want to try and build one.)
Are you stuck with those rails?
where is your 5v / 3.3v coming from?

 

Have a look at :-
http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/506853.xml
The output is isolated so you can configure tham however you want to just treat them as if they were batteries .. connecting the positive output to your ground will mean thet the negative output is now a -V rail.
you would only need 1 and your existing 5V.

Just one simple way ... there are probably loads of other solutions.

Hope this helps
Al

 

Creating a Virtual Power Supply Ground

 

I've used these in the past. Minimal parts count but very little current:

http://www.maxim-ic.com/datasheet/index.mvp/id/1357/t/al

Samples are avaialble in PDIP and surface mount.

Mouser sells a line of converters as well, totally isolated and available in many different regulated configurations.