JPS6418311A - Optical reception circuit - Google Patents

Abstract

PURPOSE:To accurately demodulate a data to be sent by discriminating the logic level independently of the offset of a reception signal through the level comparison of a 1st comparator and correcting the difference from the duty automatically by a 2nd comparator. CONSTITUTION:A photodiode 10 converts an optical signal into an electric signal and gives a signal S1 amplified via an amplifier 11 to an integration circuit comprising a resistor R4 and a capacitor C2. A comparator 13 receives an integrated signal S2 to its inverting input and a positive feedback signal S3 of its own output to the signal S1 at its noninverting input to apply level comparison between the signals S2 and S3. A voltage division circuit 14 divides the power voltage Vcc by resistors R9, R10. The 2nd comparator 15 receives a comparison output S4 of the 1st comparator 13 at its inverting input and a voltage division voltage S5 at its noninverting input respectively to apply level comparison between the signals S4 and S5. A signal S6 being the output of the 2nd comparator 15 is fed to a data processing circuit, etc., at the post- stage (not shown in figure) as the discrimination demodulation output.