OPTICAL SENSOR CIRCUIT

摘要

An optical sensor circuit which converts a sensor current flowing thorough a photoelectric transducer (PD) according to the intensity of incident light in sensing light into a voltage signal with a logarithmic characteristic in a weakly inverted state by utilizing the characteristic of a sub-threshold region of a MOS transistor (Q), and generates a sensor output corresponding to the converted voltage signal. This optical sensor circuit comprises an initializing means (1) for ridding the residual charge out of parasitic capacity prior to light sensing by the photoelectric transducer (PD). The sensor signal which has a wide dynamic range and generates no after-image even when the intensity of incident light is weak can be obtained thereby.