Stress sensor

A stress sensor array, comprising:

• a voltage supply;
• and
• a plurality of bridge circuits disposed on respective substrates and coupled between an output node and a ground node, each configured to be subjected to respective mechanical stress along at least one dimension and generate a respective voltage output, and coupled in parallel to the voltage supply, each bridge circuit of the plurality of bridge circuits comprising:
• a first branch having a first resistor having a first orientation and a first value that varies as a function of the respective mechanical stress to which its respective substrate is subjected, wherein the first resistor is coupled to a tuning resistor at a first intermediate node,
• a second branch having a second resistor having a second value and a second orientation that is different from the first orientation, wherein the second resistor is coupled to a variable resistor at a second intermediate node, wherein the variable resistor is non-linearly tunable based on the respective voltage output, and
• an amplifier having a positive input terminal coupled to the second intermediate node, and a negative input terminal coupled to the first intermediate node, wherein the amplifier is configured to generate the respective voltage output at an output node of the bridge circuit as a function of the mechanical stress applied to the substrate.

A method of measuring mechanical stress on a substrate, comprising:

• supplying a voltage supply to a bridge circuit coupled between an output node and ground, the bridge circuit comprising:
• a first branch including a first resistor having a first orientation and an impedance value that varies as a function of the mechanical stress to which the substrate is subjected, wherein the first resistor is coupled to a tuning resistor at a first intermediate node,
• a second branch including a second resistor having a second orientation that is different from the first orientation, wherein the second resistor is coupled to a switched capacitor resistor at a second intermediate node;
• comparing voltages at the first intermediate node and the second intermediate node of the bridge circuit to generate a voltage output at the output node as a function of the mechanical stress;
• and
• tuning the switched capacitor resistor in the second branch, non-linearly, using at least one of a variable frequency signal and a variable capacitance.