| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of waveform distortion in an outputted signal even when a power level of an inputted light signal is large by turning at least one of two transistors on according to a value of the outputted signal of a transformer impedance amplifier. SOLUTION: When an inputted cussent Iin becomes higher than a second reference current, the outputted voltage Vout of the transformer impedance amplifier 2 exceeds a second reference voltage V2 and the output of a second comparator 4 becomes a high level. In accordance with this, the Q terminal of a second flip-flop circuit 6 changes to a high level as well and a third MOS transistor TR2 becomes an ON state. Thus, the feedback resistor of the transformer impedance amplifier 2 becomes equivalent to the parallel resistor of a first feedback resistor R1, a second feedback resistor R3 and a third feedback resistor R4. Such operation is performed for the initial one bit after the reset signal is inputted in respective R terminals of the first and second flip-flop circuits 5. 6. |
