We all know the Differentiator and Integrator configurations of the Operational Amplifier. I realized that the RC circuits used as low pass and high pass filters can also be used as integrators and differentiators. Its obvious from their differential equations actually. As for current to voltage converter. We just need a resistor and a current source right? Than why bother making an opamp current to voltage converter? I think its called the buffer configuration. What I do not understand also is what does buffer means here? In digital circuits we may have buffer that stores binary data before it is passed on. But what does buffer mean in an analogue circuit?