Patent ID: 7466928

Claim:
An optical receiver for receiving an optical signal with a transmission rate by a semiconductor light-receiving device that outputs a photocurrent corresponding to said optical signal, comprising: a preamplifier for converting said photocurrent into a differential voltage signal, said preamplifier having a configuration of a differential amplifier to output said differential voltage signal, a main amplifier having a configuration of a differential amplifier with two inputs and two outputs for amplifying said differential voltage signal input in said two inputs and outputting from said two outputs, said main amplifier having input impedance between said two inputs, a pair of transmission lines to transmit said differential voltage signal output from said preamplifier to said main amplifier; a switching unit connected between said pair of transmission lines, wherein said transmission lines each include a capacitor to cut a DC level contained in said differential voltage signal output from said preamplifier, and wherein said switching unit is connected in parallel to said input impedance of said main amplifier to vary a low-cut frequency of said optical receiver by changing an equivalent input impedance of said main amplifier.