I connect my OpAmp with "5V to Ground config". And if i want to use +V -V configuration should i use +2,5V -2,5V to obtain an equal current?
Provide circuit of what you want to do, and why.
i am amplifying audio.
opAmps are said to need +Vcc -Vcc.
for the prototype on breadboard i use Arduino as a power supply. and it has no -V voltage. so this is the schematics of opAmp i use: http://img812.imageshack.us/img812/9043/sample2t.jpg . It has no -V as well.
also the manufacturers sign -Vcc as ground like: http://electroschematics.com/wp-content/uploads/2008/11/lm358.gif
my question is that: i read that opAmps should be fed by "+V and -V". is that the same thing to feed with "2V and ground". i think voltage difference is important. but i also read somewhere that if we do not use -V and use ground instead, negative part of the signal will be clipped during amplification. is that true?
to be clear my question is: is "2.5V ,-2,5V" connection to power lines of the opAmp same with "5V, Ground" connection?
If you are inputting an AC signal referenced to ground and ground is also the -ve connection of your amplifier then you will lose the negative portions of your signal since the signal varies both + and - relative to the ground connection.
There is a way round this and that is to simply set up a potential divider using say a couple of 10k resistors. The mid-point will be at +2.5 volts.
Now connect the return line of your AC signal source to this mid point (via a DC blocking capacitor of say 1microfarad).
Your AC input signal will now swing about the +2.5 volt reference and hence avoid clipping.
Your very basic OP amp circuit you have shown is for DC only and will not operate correctly as an audio amplifier. You will need to read up on how to configure it as such.(basically using numerous capacitors to provide DC blocking, suitable frequency response limitations etc.
Normally opamps have two power rails. You can call them 0V and 5V, or you can call them +/-2.5V - the opamp cares not what you call them, merely that it get 5V power.
A "signal ground" is the reference you compare your signal-of-interest to - if your circuit has +/- supplies you'd naturally use 0V as signal ground.
However is only "single supply" is available you'd create, as described above, an "artificial signal ground" at about halfway.
If the signal ground isn't having to drive any current (say it only goes to the inputs of opamps) then a simple resistor voltage-divider is enough. One would usually decouple this to the actual ground with a capacitor to benefit from the screening properties of the groundplane in your PCB and to "stiffen" it up against noise pick-up.
If your signal ground has to cope with non-trivial currents (more than microamps) then the usual trick is to feed your voltage divider into a unity-gain circuit using one of the op-amps to boost it to an actively regulated low impedance.
Look at the answers to your questions on the other thread that you started
on the same subject.