Hi all,

at the moment I'm trying to amplify an AUX-Signal with a 12V DC supply 
voltage. I tried die setup from here: 
http://www.mikrocontroller.net/articles/Operations... 
as u can see in the attachment.
But all I get is just an annoying noise sounding horrible.

For the amplifier I used both the CA3240EZ and the OPA134PA.

Maybe my grounds are not connected correctly.

It would be awesome, if anyone could help me out.

Mario wrote:
> Maybe my grounds are not connected correctly.

Maybe - maybe other connections are not correct. Maybe the pinout of the 
OP-Amp is different or you have mixed something up?

First part of a circuit debugging is your check whether the circuiit is 
wired accoring to plan and all components are accroding to plan. Second 
check is to check whether you have missed something in your fist check. 
Next check is an overall check: everything connected correctly, wires 
ok, ....

Have you done your three checks?

I think you can find your mistake this way on your own and learn 
something through this method.

rgds