Shielded electret transducer and method of making the same
First Claim
1. An electret transducer and preamplifier combination comprisinga pair of spaced electrodes, one said electrode being a flexible electrode so as to change the spacing between electrodes in response to force on said one electrode, the other said electrode being fixed,an electret between said electrodes,an insulator on the outer surface of the other said electrode,a conductive layer on the other side of said insulator,said conductive layer being a silicon backplate on which said electret and insulator are supported, anda preamplifier having near unity gain, said conductive layer being connected to the output of said preamplifier,whereby said conductive layer can be used to shield said other electrode to reduce stray capacitance between said other electrode and other components of said transducer.
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Accused Products
Abstract
An electret transducer including a pair of spaced electrodes, one electrode being connected to a preamplifier input, an insulator on the outer surface of the electrode connected to the preamplifier input, and a conductive layer on the other side of the insulator, whereby the conductive layer can be used to shield the electrode to reduce stray capacitance between it and other components of the transducer by connecting the conductive shield to the output of the preamplifier circuit for the transducer. Also disclosd is the use of a silicon backplate with an integrated circuit formed therein, an insulator layer thereon, a conductive layer thereon, and an electret layer thereon, the conductive layer being grounded during poling of the electret to protect the integrated circuit from damage.
68 Citations
9 Claims
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1. An electret transducer and preamplifier combination comprising
a pair of spaced electrodes, one said electrode being a flexible electrode so as to change the spacing between electrodes in response to force on said one electrode, the other said electrode being fixed, an electret between said electrodes, an insulator on the outer surface of the other said electrode, a conductive layer on the other side of said insulator, said conductive layer being a silicon backplate on which said electret and insulator are supported, and a preamplifier having near unity gain, said conductive layer being connected to the output of said preamplifier, whereby said conductive layer can be used to shield said other electrode to reduce stray capacitance between said other electrode and other components of said transducer.
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5. An electret transducer and amplifier circuit comprising
transistor having source, gate and drain nodes, a pair of spaced electrodes, one said electrode being connected to said gate, another said electrode being connected to one of said drain and source, a said electrode being a flexible electrode so as to change the spacing between electrodes in response to force on said flexible electrode, an electret between said electrodes, and a conductive member spaced from the outer surface of said one electrode being connected to said gate, said conductive member being connected to the other of said drain and source.
Specification