c1

Non-inverting, unity-gain buffer/voltage follower. The op-amp tries to keep the inverting (negative) input at the same voltage as the non-inverting (positive) input, therefore outputs the same voltage as the non-inverting (positive) input. The operational amplifier provides impedance bridging by presenting a very high input impedance to the input circuit, and a very low output impedance to the output circuit. In this way, the op-amp can provide high output current when the input circuit is unable to do so.