| 摘要 |
PROBLEM TO BE SOLVED: To provide a light-reception amplifier circuit which prevents the deterioration in S/N ratios of output signals by reducing heat noise without narrowing an output voltage range. SOLUTION: The light-reception amplifier circuit 1a is provided with; a preamplifier circuit 2 to which a light-receiving element PD is connected; a preamplifier circuit 3 which is separated from the light-receiving element PD and is the same type as the preamplifier circuit 2; and a differential amplifier circuit 8a which amplifies an output voltage difference between the preamplifier circuit 2 and the preamplifier circuit 3. In this case, the preamplifier circuit 2 has an amplifier A1 and feedback resistors RfH1 and RfH2, and the one ends of the feedback resistors RfH1 and RfH2 are connected in common to the input terminal of the amplifier A1. In addition, the amplification rate of the differential amplifier circuit 8a is smaller than 1. Further, the preamplifier circuit 2 is provided with an output voltage expansion circuit 4 which is connected to the other end of the feedback resistor RfH1 of the preamplifier circuit 2 and to the output terminal of the amplifier A1, expands a range of an output voltage from the amplifier A1, and supplies the differential amplifier circuit 8a with the output voltage. COPYRIGHT: (C)2007,JPO&INPIT
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