Electronic Device with Noise-Cancelling Force Sensor
First Claim
1. An electronic device, comprising:
- a strain gauge having at least one variable resistor; and
a differential amplifier that receives signals from the at least one variable resistor.
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Accused Products
Abstract
An electronic device may have a housing in which components such as a display are mounted. A strain gauge may be mounted on a layer of the display such as a cover layer or may be mounted on a portion of the housing or other support structure. The layer of material on which the strain gauge is mounted may be configured to flex in response to pressure applied by a finger of a user. The strain gauge may serve as a button for the electronic device or may form part of other input circuitry. A differential amplifier and analog-to-digital converter circuit may be used to gather and process strain gauge signals. The strain gauge may be formed form variable resistor structures that make up part of a bridge circuit that is coupled to the differential amplifier. The bridge circuit may be configured to reduce the impact of capacitively coupled noise.
98 Citations
29 Claims
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1. An electronic device, comprising:
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a strain gauge having at least one variable resistor; and a differential amplifier that receives signals from the at least one variable resistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An electronic device, comprising:
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a layer of material having an inner surface and an outer surface; variable resistor structures on the inner surface, wherein the variable resistor structures form part of a strain gauge bridge circuit; and a differential amplifier having a first differential input that receives signals from the variable resistor structures and a second differential input that receives signals from the variable resistor structures and that produces a corresponding output signal that is responsive to strain in the layer of material. - View Dependent Claims (22, 23, 24)
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25. A strain gauge, comprising:
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a layer of material on an electronic device that is configured to flex in response to pressure from a finger of a user; variable resistor structures mounted on the layer of material; and a differential amplifier having first and second differential inputs that receive input from a bridge circuit and having an output at which a corresponding strain gauge output signal is provided, wherein the variable resistor structures form at least part of the bridge circuit and wherein the variable resistor structures are configured to balance how much noise is capacitively coupled from the finger of the user to the first differential input of the differential amplifier through the variable resistor structures with how much noise is capacitively coupled from the finger of the user to the second differential input of the differential amplifier through the variable resistor structures to reduce noise in the strain gauge signal at the output of the differential amplifier. - View Dependent Claims (26, 27, 28, 29)
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Specification