> 4.1 | General Usage of Microphone Interface 1 and 2

> The microphone interfaces MIC1 and MIC2 are identical. MIC1 corresponds to EP1 and MIC2 corresponds to EP2, respectively (see also Figure 1).
> To reduce or increase the gain of the module you may use the AT^SNFI command (compare Section 6.3.3).
> Biasing is needed for the input voltage either MICPx or MICNx.
> Recommended bias voltage: 1.0V … 1.6V
> Figure 10 and Figure 11 show two examples in which the bias is derived from the internal voltage supply VMIC via a simple resistor network. The voltage VMIC needs filtering. The filter can be realized as a simple first order RC-network (Figure 10, Figure 11: R1 and C1).

> Figure 10: Recommended values for a typical electret microphone | Figure 11: Recommended values for line input configuration with OpAmp