A circuit diagram of a buffer amplifier made using an operational amplifier.

${\displaystyle V_{\mathrm {out} }=V_{\mathrm {in} }\!\ }$

${\displaystyle Z_{\mathrm {in} }=\infty }$ (realistically, the differential input impedance of the op-amp itself, 1 MΩ to 1 TΩ)