Capacitive sensor assemblies and electrical circuits therefor
AssigneeKnowles Electronics, LLC
InventorsMichael Jennings, Dean Badillo
Life of this patent
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Abstract
A sensor assembly including a capacitive sensor, like a microelectromechanical (MEMS) microphone, and an electrical circuit therefor are disclosed. The electrical circuit includes a first transistor having an input gate connectable to the capacitive sensor, a second transistor having an input gate coupled to an output of the first transistor, a feedforward circuit interconnecting a back-gate of the second transistor and the output of the first transistor, and a filter circuit interconnecting the output of the first transistor and the input gate of the second transistor.
Claims20
An electrical circuit for a capacitive sensor assembly, the circuit comprising:
- a first transistor having an input gate connectable to a capacitive sensor;
- a second transistor having an input gate coupled to an output of the first transistor, the second transistor including a back-gate;
- a feedforward circuit interconnecting the back-gate of the second transistor and the output of the first transistor;
- and
- a filter circuit interconnecting the output of the first transistor and the input gate of the second transistor,
- wherein the feedforward circuit bypasses the filter circuit.
An integrated circuit for a capacitive microelectromechanical systems (MEMS) microphone assembly, the circuit comprising:
- a first transistor configured as a source-follower comprising an input gate connectable to an output of a capacitive MEMS die, and a source coupled to an output of the first transistor;
- a second transistor configured as a source-follower comprising an input gate coupled to the output of the first transistor, a source coupled to an output of the second transistor, and a back-gate electrically coupled to the output of the first transistor;
- an audio band filter circuit interconnecting the output of the first transistor and the input gate of the second transistor;
- a DC bias circuit having a reference signal output coupled to the input gate of the first transistor by a resistance element, the reference signal output of the DC bias circuit coupled to the input gate of the second transistor by a resistance element,
- the circuit having an input capacitance on the order of 0.1 pF.
A microphone sensor assembly comprising:
- a housing having an external-device interface and a sound port;
- a capacitive microelectromechanical systems (MEMS) die disposed in the housing and acoustically coupled to the sound port;
- an integrated circuit disposed in the housing and electrically coupled to contacts on the external-device interface, the circuit comprising:
- a first transistor having an input gate coupled to a first node of the capacitive MEMS die;
- a second transistor having an input gate coupled to an output of the first transistor, the second transistor including a back-gate;
- a feedforward circuit interconnecting the back-gate of the second transistor and the output of the first transistor;
- a filter circuit interconnecting the output of the first transistor and the input gate of the second transistor;
- and
- a MEMS die bias circuit coupled to a second node of the capacitive MEMS die.
Dependencies are inferred from the claim text.