Contents I. Introduction
During the last years the demand for MEMS microphones with an increased range of linearity has grown, following the needs of the consumer market, especially in those applications regarding video recording on smartphones. A differential MEMS sensor [1] [2] is the most common and effective way to solve this design challenge because it is able to produce half the signal at the input stage of the system, thus extremely relaxing its linearity specs. But this evident advantage comes, of course, with a cost, in terms of fabrication and industrialization complexity, not to mention the need to electronically compensate the natural spread in the sensitivity of the two channels, which is far than negligible. This, in the end, increases the cost of the overall system. On the other hand, for those systems where a high dynamic range is required, the use of differential sensors is necessary since a single backplate sensor, providing a single ended input signal, saturates the readout input stages when the acoustic signal is slightly above 120dBSPL. A 135dBSPL dynamic range analog MEMS Capacitive Microphone system is presented. The innovative readout system makes possible to achieve differential mode operation at the input stage, so very high linearity, although employing a single membrane sensor, hence reducing the system complexity and costs without losing in noise performances.
