AN-0284 – Low-Noise Directional Studio Microphone Reference Design

AN-0284 – Low-Noise Directional Studio Microphone Reference Design

Circuit Description

An array of many INMP411 MEMS microphones are closely spaced in this circuit to improve the overall SNR of the system to a point that it can be used for very low noise recording studio applications. The circuit can be used with either one or two clusters of microphones, depending on the desired directionality. Using two microphone arrays and some simple filtering enables some basic beamforming to achieve a supercardioid directional response; while the directional response of a single microphone array is basically omnidirectional, like the response of a single MEMS microphone.

Following the summing, filtering, and beamforming, the signal is still single-ended. The AD8273 difference amplifier converts this single-ended signal into a differential signal that is output on the XLR jack. This circuit can be powered from a single 9 V battery, and two regulators generate the ±9 V and +1.8 V supplies. The amplifiers use the bipolar supply, while the MEMS microphones operate from the single low-voltage 1.8 V supply.

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