Photodector including photodiodes having improved dynamic range, s/n ratio and speed of light detection

摘要

The present invention aims at providing a photodetector which can improve each of the dynamic range, S/N ratio, and speed of light detection. A photodiode PD_m,n generates electric charges by an amount corresponding to the incident light intensity, and accumulates thus generated electric charges into a junction capacitance part. An electric charge amount level determining circuit 10 _m,n determines the level of amount of electric charges generated by the photodiode PD_m,n and accumulated in the junction capacitance part. In an integrating circuit 20 _m, the capacitance value of an integral capacitance part 21 is set according to the result of electric charge amount level determination, the electric charges inputted from the photodiode PD_m,n by way of a switch SW 1 _m,n are accumulated into the integral capacitance part 21, and a voltage V₂₀ corresponding to the amount of thus accumulated electric charges is outputted. The voltage V_inp fed to a non-inverting input terminal of an amplifier A in the integrating circuit 20 _m is set greater in a second period during which the integral capacitance part 21 of the integrating circuit 20 _m accumulates electric charges than in a first period during which the junction capacitance part of the photodiode PD_m,n accumulates electric charges.