Preamplifier circuit for a microelectromechanical capacitive acoustic transducer

A readout-interface circuit, comprising:

• a preamplifier circuit configured to receive a capacitive variation signal from a MEMS detection structure and to amplify the capacitive variation signal, the preamplifier circuit including:
• a reference capacitive element coupled to the MEMS detection structure, the reference capacitive element having a value of capacitance substantially equal to a value of capacitance at rest of the MEMS detection structure;
• an amplification stage configured to generate a differential output signal based on the capacitive variation signal, the amplification stage including a fully differential amplifier having a first input coupled to the MEMS detection structure and a second input coupled to the reference capacitive element, the fully differential amplifier being configured to receive and to amplify the capacitive variation signal;
• and
• a reference generator circuit coupled to an internal node of the differential amplifier and configured to supply a biasing quantity to the internal node of the differential amplifier and to generate said biasing quantity proportional to a reference voltage.

An acoustic transducer, of a capacitive type, comprising:

• a microelectromechanical detection structure configured to generate a capacitive variation signal as a function of an acoustic signal;
• and
• a readout-interface circuit coupled to the microelectromechanical detection structure, the readout-interface circuit including:
• a reference capacitive element having first and second terminals, the first terminal being coupled to the microelectromechanical detection structure;
• a differential amplifier having a first differential input coupled to the microelectromechanical detection structure, a second differential input coupled to the second terminal of the reference capacitive element, first and second differential outputs and an internal node, the differential amplifier being configured to generate a differential output signal based on the capacitive variation signal;
• and
• a reference generator circuit coupled to the internal node of the differential amplifier and configured to supply a biasing quantity to the internal node of the differential amplifier and to generate said biasing quantity proportional to a reference voltage.

A device comprising:

• a microprocessor control unit;
• and
• an acoustic transducer coupled to said microprocessor control unit, the acoustic transducer including:
• a MEMS detection structure configured to generate a capacitive variation signal as a function of an acoustic signal;
• and
• a readout-interface circuit coupled to the MEMS detection structure, the readout-interface circuit including:
• a reference capacitive element coupled to the MEMS detection structure, the reference capacitive element having a value of capacitance substantially equal to a value of capacitance at rest of the MEMS detection structure;
• an amplification stage configured to generate a differential output signal correlated to said capacitive variation signal, the amplification stage including a fully differential amplifier having a first input coupled to the MEMS detection structure and a second input coupled to the reference capacitive element, the fully differential amplifier being configured to amplify said capacitive variation signal, the differential amplifier including an internal node;
• and
• a reference generator circuit coupled to the internal node of the differential amplifier and configured to supply a biasing quantity to the internal node of the differential amplifier and to generate said biasing quantity proportional to a reference.