Re: what is the requirement of the opamp for an opamp buffer
As a output buffer with opamp, it is closed loop with unity gain.
It is the voltage-voltage feeback type. therefore, this results in the close loop large input impedence and small output impedence. So the configure is fit for inteface as a buffer.
After close loop, the input impedence is
Rin=Rin0*(1+Aβ)
the output impedence is
Rout=Rout0/(1+Aβ)
the BandWith is
UBW=UBW0*(1+Aβ)
So maybe depending on you application, you can select the open gain ,the open loop input impdence ,output impdence and bandwith.