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

Abstract

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 PDgenerates 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 circuitdetermines the level of amount of electric charges generated by the photodiode PDand accumulated in the junction capacitance part. In an integrating circuit, the capacitance value of an integral capacitance partis set according to the result of electric charge amount level determination, the electric charges inputted from the photodiode PDby way of a switch SWare accumulated into the integral capacitance partand a voltage Vcorresponding to the amount of thus accumulated electric charges is outputted. The voltage Vfed to a non-inverting input terminal of an amplifier A in the integrating circuitis set greater in a second period during which the integral capacitance partof the integrating circuitaccumulates electric charges than in a first period during which the junction capacitance part of the photodiode PDaccumulates electric charges.