| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an amplifier having both initial response speed characteristics and stability characteristics. <P>SOLUTION: A part of a current signal obtained by photoelectric conversion by a PD 111 is subtracted by a current source 112 and the residue is input into an amplifier 120. In the amplifier 120, an impedance conversion amplifier 121 converts the current signal into a voltage signal, and an amplifier 123 amplifies the voltage signal. A signal detector 124 detects the presence or absence of the voltage signal, and an automatic offset compensation circuit 125 integrates the voltage signal. If it is detected that the voltage signal is not present, the automatic offset compensation circuit 125 integrates the signal at a small time constant, and if it is detected that the voltage signal is present, the automatic offset compensation circuit 125 integrates the signal at a large time constant. A subtracting amount by the current source 112 is controlled depending on an output (integration value) of the automatic offset compensation circuit 125. <P>COPYRIGHT: (C)2010,JPO&INPIT |
