Fingerprint sensing device with common mode suppression
First Claim
1. A fingerprint sensing device for sensing a fingerprint pattern of a finger, said fingerprint sensing device comprising:
- a plurality of electrically conductive sensing structures including at least a first sensing structure and a second sensing structure; and
charge sensing circuitry connected to said sensing structures, said charge sensing circuitry including a set of charge amplifiers comprising at least a first charge amplifier and a second charge amplifier, each comprising;
a first input;
a second input;
an output; and
at least one amplifier stage between said first and second inputs, and said output,said output being capacitively coupled to said first input,wherein;
the first input of said first charge amplifier is connected to said first sensing structure;
the first input of said second charge amplifier is connected to said second sensing structure; and
the output of said first charge amplifier is capacitively coupled to the first input of said second charge amplifier,wherein the output of said second charge amplifier is capacitively coupled to the first input of said first charge amplifier.
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Abstract
The present invention relates to a fingerprint sensing device for sensing a fingerprint pattern of a finger, the fingerprint sensing device comprising at least a first sensing structure and a second sensing structure; and at least a first charge amplifier and a second charge amplifier. Each charge amplifier comprises: a first input; a second input; an output; and at least one amplifier stage between the first and second inputs, and the output. The output is capacitively coupled to the first input. The first input of the first charge amplifier is connected to the first sensing structure; the first input of the second charge amplifier is connected to the second sensing structure; and the output of the first charge amplifier is capacitively coupled to the first input of the second charge amplifier to suppress the common mode component.
9 Citations
15 Claims
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1. A fingerprint sensing device for sensing a fingerprint pattern of a finger, said fingerprint sensing device comprising:
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a plurality of electrically conductive sensing structures including at least a first sensing structure and a second sensing structure; and charge sensing circuitry connected to said sensing structures, said charge sensing circuitry including a set of charge amplifiers comprising at least a first charge amplifier and a second charge amplifier, each comprising; a first input; a second input; an output; and at least one amplifier stage between said first and second inputs, and said output, said output being capacitively coupled to said first input, wherein; the first input of said first charge amplifier is connected to said first sensing structure; the first input of said second charge amplifier is connected to said second sensing structure; and the output of said first charge amplifier is capacitively coupled to the first input of said second charge amplifier, wherein the output of said second charge amplifier is capacitively coupled to the first input of said first charge amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of sensing a fingerprint pattern of a finger using a fingerprint sensing device comprising:
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a plurality of electrically conductive sensing structures including at least a first sensing structure and a second sensing structure; and charge sensing circuitry connected to said sensing structures, said charge sensing circuitry including at least a first charge amplifier and a second charge amplifier, each comprising; a first input; a second input; an output; and at least one amplifier stage between said first and second inputs, and said output, said output being capacitively coupled to said first input, wherein said method comprises the steps of; providing a capacitive coupling between the output of the first charge amplifier and the first input of the second charge amplifier; providing a capacitive coupling between the output of the second charge amplifier and the first input of the first charge amplifier; sampling outputs of said first and second charge amplifiers to form a representation of said fingerprint pattern.
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Specification