Patent ID: 7663089

Claim:
A receiving apparatus comprising: a light receiving element which receives an optical signal and generates a current signal dependent on the optical signal; a conversion unit which converts the current signal into a voltage signal; a reference voltage generation unit which generates a reference voltage; a threshold voltage generation unit which generates a threshold voltage signal based on the voltage signal outputted from the conversion unit and the reference voltage outputted from the reference voltage generation unit, the threshold voltage having different voltage levels between a rising and a falling of the voltage signal; and a comparison unit which compares the voltage signal outputted from the conversion unit with the threshold voltage signal outputted from the threshold voltage generation unit, wherein the threshold voltage generation unit includes: a level shift circuit which subtracts an offset voltage from the voltage signal and thereby lowers the voltage signal by the offset voltage; a peak hold circuit which is connected to an output terminal of the level shift circuit and holds a peak voltage of the voltage signal being the result of subtracting the offset voltage at a desired time constant; a resistor which is connected between an output terminal of the reference voltage generation unit and an output terminal of the peak hold circuit; and a current source circuit which is connected to the output terminal of the peak hold circuit and causing the offset voltage to be generated between both terminals of the resistor.