OFFSET SWITCHING TYPE OPTICAL RECEPTION CIRCUIT

PURPOSE:To attain an offset switching type optical reception circuit stable against noise by varying an offset voltage. CONSTITUTION:An offset generating circuit 5 giving a preset reference signal level and a signal comparator 7 comparing the two signal levels of an input signal and an output signal of the circuit 5 are provided, and an AC component detection circuit 4 connected in parallel with the input signal line and extracting the AC component, a comparator 8 connected in series with the detection circuit 4 and comparing the output of the circuit 4 with the preset reference electric signal level, and an offset control circuit 6 controlled by the output of the comparator 8 and controlling the electric signal level of the offset generating circuit 5 are provided. Thus, the offset voltage is made variable and the optical reception circuit stable against noise and having no output distortion is obtained.