Piezoelectric (Piezoelectric), piezo-resistive type (Piezoresistive) and capacitance (Capacitive) is a common micro microphone technology at present. Piezoelectric microphone after using piezoelectric materials mechanical characteristics of the output current or voltage, convert voice signal into electrical signal, after amplification and output, and pressure resistance type microphone is the use of pressure resistance materials after the stress resistance characteristics change. Usually the two microphone sensitivity to the sound pressure is low, and the system noise is bigger. Because the capacitance decay microphone has Gao Gan and fine properties such as low power consumption, is the mainstream in the development of the market at present.

Capacitive microphone structure mainly use two pieces of the conductive plate and the air layer to form a basic insulation between the two plate capacitor structure, the two pieces of the conductive plate are usually referred to as "diaphragm" (be) and "lagging" (the Backplate). Ideal vibration membrane is an extremely soft elastic film, under pressure will produce vibration, thus change of micro distance, cause dynamic micro displacement between the diaphragm and the backboard, thus making the structure of the capacitance value is changed.

Structure of capacitive microphone: MEMS microphone sensor chip structure is usually composed of a layer of thin and low stress compound crystal silicon or silicon nitride formation of diaphragm, the other with a thicker or compound crystal silicon metal layer to form a porous structure of the backboard, together form a group to the trimmer capacitor structure of air as a dielectric layer. Except necessary MEMS sensor in encapsulation on MEMS microphones usually still must match the other circuit wafer, provide the MEMS chips during normal operation and will need the stability of the bias, the signal after dealing with the amplification output, general loosely called ASIC (Application Specific IC).

MEMS microphone sensor chip structure diagram: MEMS microphone using ASIC by product category is different, divided into analog and digital two paragraphs. Analog ASIC its basic architecture is mainly by "doubler circuit" (Charge Pump), the Voltage stabilizer (Voltage Regulator) and "amplifier" (Amplier) three big functions of block circuit.

Doubler circuit purpose is through to pressurize the input power, in order to provide higher operating voltage of the MEMS chips needed. Function is magnified and stable input signal amplifier circuit. The function of the voltage stabilizer is provided on the ASIC power input end voltage stabilizing treatment, make the chip inside the circuit blocks are functioning normally. Digital ASIC and in addition to have a combination of the above three basic function block, also increases the so-called "triangular" integral modulation device (Sigma Delta Modulator) circuit, to be responsible for the signal sampling and suppress noise.