How can I estimate the output impedance of a unity-gain opamp buffer circuit?
With an ideal opamp the impedance would be \$0 \Omega\$, but we don't have ideal parts. E.g. the datasheet of the AD8226 instrumentation amplifier recommends a source impedance below of \$2 \Omega\$ as voltage reference. The example uses the OP1177 opamp to realize a buffer circuit. How do I know that the choosen opamp fulfills the design constraint or how would I choose a suitable opamp?