Temperature Compensating Transparent Force Sensor Having a Complliant Layer

An electronic device comprising:

• an touch-sensitive surface;
• a force sensor positioned below the touch-sensitive surface and comprising:
• a first strain-sensitive element;
• a compliant layer disposed below the first strain-sensitive element;
• and
• a second strain-sensitive element below the compliant layer and electrically coupled to the first-strain sensitive element;
• and
• a sensor circuit configured to obtain a differential measurement of a first electrical response of the first strain-sensitive region and a second electrical response of the second strain-sensitive region;
• wherein
• the differential measurement changes in response to a force applied to the touch-sensitive surface.

An electronic device comprising:

• a cover defining an touch-sensitive surface;
• a force sensor positioned below the cover and comprising a strain-sensitive element configured to deform in response to a force applied to the touch-sensitive surface;
• and
• a sensor circuit configured to obtain a differential measurement between a first electrical response of the strain-sensitive element and a second electrical response of a resistive element electrically coupled to the strain-sensitive element;
• wherein
• the resistive element is formed from the same material as the strain-sensitive element;
• and
• the resistive element is thermally coupled to the strain-sensitive element.

A force sensor for an electronic device, comprising:

• a first substrate layer comprising a first array of strain-sensitive elements;
• a second substrate layer comprising a second array of strain-sensitive elements, each strain-sensitive element of the second array of strain-sensitive elements electrically coupled to a respective strain-sensitive element of the first array of strain-sensitive elements, thereby defining an array of strain-sensitive element pairs;
• a compliant layer separating the first substrate layer from the second substrate layer;
• and
• a sensor circuit configured to obtain a differential measurement from at least one strain-sensitive element pair;
• wherein
• the differential measurement changes in response to a force applied to a touch-sensitive surface adjacent to the at least one strain-sensitive element pair.