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An amplifier that converts input charge to voltage through a feedback capacitance; used to read a piezoelectric stress sensor while controlling electrical loading.

Piezoelectricity is linear coupling between mechanical deformation and electrical response in suitable materials. The direct piezoelectric effect produces electrical polarization under applied stress; the converse piezoelectric effect produces strain under an applied electric field. The two responses are linked by the same electromechanical coupling coefficients when conventions and mechanical constraints are specified consistently.

A piezoelectric stress sensor uses the direct response to turn force or vibration into an electrical signal. A scanning probe uses the converse response to move a tip by very small distances, controlling a tunnel junction's separation. The resulting displacement can depend on drive history through piezoelectric hysteresis and can continue changing after a voltage step through piezoelectric scanner creep. These effects motivate calibration and closed-loop control.