| 摘要 |
PROBLEM TO BE SOLVED: To decrease the circuit scale of optical reception equipment by connecting one terminal of a two-terminal type variable resistor, whose impedance is changed by an inter-terminal voltage, to the output of a signal amplitude detector and connecting the other terminal to the output of an optoelectrical converter. SOLUTION: If the peak value of an optical signal is increased, the output of a level converter 11 is changed to a low-order voltage side, and when the output of the level converter 11 is changed to a low-order voltage side, the inter-terminal voltage of a two-terminal type variable resistor 20 is increased. At this time, the two-terminal type variable resistor 20 is changed to a low-impedance side, and one part of a signal current outputted from an optoelectrical converting element 2 flows to the two-terminal type variable resistor 20. Namely, even in the case of the maximum input amplitude of an optical signal for starting the saturation of an internal circuit of an amplifier 3 in the absence of a signal amplitude detector 7 and of the two-terminal type variable resistor 20, the signal current to flow to the amplifier 3 is decreased by the signal amplitude detector 7 and two-terminal type variable resistor 20. Consequently, the maximum input amplitude of the optical signal for starting the saturation of the internal circuit of the amplifier 3 can be expanded. |
