Patent ID: 6760552
Filing Date: 2004-07-06
Classification: H04B

Abstract:
An optical receiving circuit comprising:a preamplifier circuit connected to a photodetector, said preamplifier circuit receiving photo current from said photodetector; an output differential amplifier coupled to the preamplifier circuit, the output differential amplifier receiving a voltage output from said preamplifier circuit; and a reference voltage generating circuit coupled to said differential amplifier and coupled to said preamplifier circuit, said reference voltage generating circuit generating a reference voltage based upon a mean value per time of said voltage output from said preamplifier circuit, said reference voltage generating circuit supplying said reference voltage to said output differential amplifier, wherein said reference voltage generating circuit includes: a sample-hold circuit; an output voltage holding circuit holding said voltage output from said preamplifier circuit; a digital value holding circuit coupled to the output voltage holding circuit, the digital value holding circuit holding an output of said output voltage holding circuit as a digital value; and a voltage selecting circuit coupled to said digital value holding circuit, the voltage selecting circuit selecting said reference voltage from a plurality of predetermined voltages based upon said digital value voltage held by said digital value holding circuit.