| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent the deterioration of an output waveform or the destruction of a transimpedance amplifier when a large current or a current exceeding an input permission current is inputted to the transimpedance amplifier. <P>SOLUTION: When a current inputted to the transimpedance amplifier 12 is a large current or when an optical signal of a level which exceeds a permission input level of the transimpedance amplifier and destroys the transimpedance amplifier is inputted to a photoelectric conversion amplifier circuit 5, a feedback resistance value in the transimpedance amplifier is dropped by a control signal created in an optical level detection part 10, or a current flowing in a feedback resistor in the transimpedance amplifier is reduced. Thus, the deterioration of the output waveform of the photoelectric conversion amplifier circuit is prevented. Then, a voltage between a gate and a source of the transimpedance amplifier is set to be within an allowance, and the destruction of the transimpedance amplifier is prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
