I have an unipolar DAC with a range from 0V to 3V, now I must connect this DAC with a operational amplifier but I need a bipolar OA output voltage (like from -15 to +15)... What can I use ???
Use an opamp with bipolar supply ..
Below you can see an example on how to convert one voltage to another; in this cas it is from 0-5 to 5-0, but with similar circuits you can produce any output range you may need ..