Photodetector apparatus

A photodetector apparatus comprising a photosensitive section which has a photodiode for converting an inputted optical signal into a current signal and outputs said current signal, said photodetector apparatus comprising:

• (A) an integrating circuit including a first full differential amplifier, having first and second input terminals and first and second output terminals, for feeding said current signal from said photosensitive section into said first input terminal;
• an additional capacitor, having a capacitance substantially equal to a junction capacitance of said photodiode, connected to said second input terminal of said first full differential amplifier;
• a first capacitor disposed between said first input terminal and first output terminal of said first full differential amplifier;
• a first switch disposed in parallel with said first capacitor;
• a second capacitor disposed between said second input terminal and second output terminal of said first full differential amplifier;
• and a second switch disposed in parallel with said second capacitor;
• said integrating circuit inputting and integrating said current signal outputted from said photosensitive section, and outputting integral signals corresponding to a result of integration from said first and second output terminals of said first full differential amplifier, respectively;
• and
• (B) a differential amplifier circuit for inputting said respective integral signals outputted from said first and second output terminals of said first full differential amplifier in said integrating circuit and outputting, according to a difference therebetween, a signal corresponding to an intensity of said optical signal.