Does any one know why the use if this buffer in the circuit? because I think there is no filter!!
Could anyone explain this please.
Thanks and best regards
Best Answer
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.
Would any old op-amp/buffer with a shutdown signal be sufficient? Digikey has TONS of options if this is acceptable. MAX9812 is a SC70-6 package, for example. (Not a buffer. LMV341 is a single op-amp with shutdown in an SC70-6 package.)
If the datasheet says it is unity gain stable, then yes. Unity gain stable means precisely that the op-amp will be stable when used as you describe.
Do be sure the feedback path is short. If you make it long, then its inductance is increased, and maybe weird things will happen. No need to be extremely paranoid on this point; just don't go routing it 10 inches around the board and you should be fine.
Best Answer
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.