App note from TDK on design considerations of preamps used on MEMS microphones. Link here
A microphone preamp circuit is used to amplify a microphone’s output signal to match the input level of the devices following it in the signal chain. Matching the peaks of the microphone’s signal level to the full-scale input voltage of an ADC makes maximum use of the ADC’s dynamic range and reduces the noise that subsequent processing may add to the signal.