OPTICAL SENSOR CIRCUIT AND IMAGE SENSOR USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide the pixel with a large opening ratio and excellent sensitivity. SOLUTION: This optical sensor circuit is provided with a photoconductive film L1 for converting optical signals to a sensor current, a MOS transistor Q1 for converting the converted sensor current to a detection voltage provided with logarithmic characteristics in a weak inversion state, a capacitor C connected to the detection terminal of the MOS transistor and a gate voltage VG for applying a voltage for reset to the gate voltage of the MOS transistor at the time of detecting the optical signals thereby lowering impedance between a drain and a source and controlling the charging or discharging of the capacitor. The optical sensor circuit is also provided with a linear response area for detecting the detection voltage proportional to the charging current or discharging current of the capacitor C in the case that the sensor current converted by the photoconductive film L1 is equal to or less than a prescribed current and further it is provided with a logarithmic response area for detecting the detection voltage having logarithmic characteristics corresponding to the load characteristics of the MOS transistor Q1 in the case that the sensor current converted by the photoconductive film L1 is a current exceeding the prescribed level.