An optical proximity sensor comprises a solid-state photo-electric converter, a biasing circuit for biasing the solid-state photo-electric converter, and a drive circuit. The drive circuit is configured to control the biasing circuit to apply to the photo-electric converter a bias signal modulated between a first value and a second value, the second value different from the first value, wherein a modulated optical signal is emitted by the solid-state photo-electric converter towards a target object. The drive circuit is configured to receive an electrical output signal from the solid-state photo-electric converter, the electrical output signal being a function of a modulated optical signal received at the solid-state photo-electric converter as a result of reflection of the emitted modulated optical signal at the target object. The drive circuit is configured to perform a phase comparison of the modulated bias signal against the electrical output signal and produce, as a result of the phase comparison, a phase shift signal. The drive circuit is configured to compute a distance between the optical proximity sensor and the target object as a function of the phase shift signal.