| 摘要 |
PURPOSE:To apply binary-coding even to an optical signal minute in amplitude and to restore correctly the pulse width by providing a light receiving circuit having a wide dynamic range and less pulse distortion in which specific resistance values are used and capacitors of small capacitance only are employed so as to form a one-chip monolithic IC. CONSTITUTION:The titled circuit is formed as a one-chip integrated circuit except an externally mounted capacitor Cext. A voltage signal (b) is differentiated once so as to eliminate the DC component in the circuit. A signal (d) is obtained by retarding one of the signals and a differentiation signal (e) is obtained by applying differential amplification between the signal (d) and an original signal (c) in the differentiating circuit. The differentiating signal (e) is given to a base of a Q9, where the signal is subject to current amplification. A transistor (TR)Q41 connected to the emitter of the Q9 and a resistor R28 form a constant current circuit. The base voltage is given by R23 and R24. The level of the emitter (f) of the Q9 is lower than the level of the (e) by the base-emitter drop. In order to binary-code the signal (f), the mean value of the (f) is obtained and the (f) and the mean value of the (f) are amplified differentially. Thus, the dynamic range is widened and the problem of offset is eliminated. |
