| 摘要 |
PROBLEM TO BE SOLVED: To suppress the deterioration in the clock duty of a preamplifier for light reception with wide dynamic range characteristics. SOLUTION: An invertible amplifier circuit 13, a feedback resistor 14, and a shunt transistor 15 are so arranged as to obtain an output voltage Vout, which varies between a base voltage Vbase corresponding to the off level of light and a peak voltage Vpeak corresponding to the on level of the light according to an input current Iin. When the input current Iin is large, a current Id flowing to the shunt transistor 15 is converted into an offset voltage Vof by a resistor 22 connected to the output terminal of a current mirror 21. A peak detector 24 supplies a corrected peak voltage Vpeak-Vof obtained by detecting the peak value Vpeak of the output voltage Vout and correcting the peak value with the offset voltage Vof. A voltage dividing circuit 26 generates a reference voltage Vref used to determine the logical value of the output Vout, in accordance with a reference voltage generating equation Vref=(Vbase+(Vpeak-Vof)/2. |
