Does any one know why the use if this buffer in the circuit? because I think there is no filter!!
The output from the mic which comes in on
MIC_IN_FA_P is going to have a relatively high impedance, i.e., it won't be able to drive very much current. The buffer amplifier is able to convert a low current on the input to a higher current on the output.
C1735 AC-couples the
MIC_IN_FA_P line to the DC bias, which is presumably in place so that the amp can be powered with only a single +DC rail. Similarly, C1742 AC-couples the output of the buffer to wherever it goes.
Typically a current buffer amplifier is used to transfer a current from a first circuit, having a low output impedance level, to a second circuit with a high input impedance level.