Robert Boschgmbh

Akustica, Inc.

Anthony T Zisko

John Matthew Muza

Matthew A Zeleznik

A biasing circuit for a capacitive sensor includes a capacitive sensor element configured to produce a sensor voltage at a sense node, and a preamplifier connected to the sense node and configured to amplify the sensor voltage. The biasing circuit has an auxiliary amplifier connected between an output of the preamplifier and the sense node and configured to set a DC component of an input voltage for the preamplifier to a ratiometric DC bias voltage.

Ratiometric biasing for high impedance capacitive sensing

Systems and methods are presented for power supply noise cancellation in a microphone package. A first node on a MEMS microphone package is coupled to an inverted voltage signal of a power supply output. A summing node is connected to both the first node and a second node. The second node is coupled to a non-inverted voltage signal of the power supply output. Because the parasitic capacitance of the MEMS microphone package is substantially equivalent relative to both the first node and the second node, the summing node outputs a noise-reduced summed voltage signal. An adjustable trim module is coupled to the first node and configured to adjust a reduction of a power supply noise in the summed voltage signal from the summing node.

Elimination of 3D parasitic effects on microphone power supply rejection

A MEMS microphone package is described that includes a first node and a second node having nearly equivalent 3D parasitic capacitances relative to a preamplifier of the microphone package, such that any noise generated on the first node is equivalent to any noise generated on the second node. An external power supply is connected to the first node and provides a bias voltage signal to the MEMS microphone package via the first node. An inverting amplifier is connected between the power supply and the second node. A third node is connected to the first node through a packaging parasitic capacitor, while the second node is connected to the third node through either an intended parasitic capacitor or an explicit capacitor. The noise coupled from the external power supply to the third node is then cancelled by summing the inverted power supply noise into the third node.

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Pittsburgh, PA, United States of America

Anthony T Zisko