| 摘要 |
A received-light amplifying circuit includes: an amplifier AMP1 converting a current signal provided from a light-receiving element into a voltage signal; differential voltage amplifying circuits AMP2 and AMP3 each of which has a non-inverting input terminal connected to the AMP1; an output connected commonly to the AMP2 and the AMP3; feedback resistors R2 and R4 connected between the output and one of inverting inputs of the AMP2 and the AMP3 respectively; gain resistors R1 and R3 connected between a reference voltage and the one of inverting inputs respectively; a switch SW1 connected, between the output and the reference voltage, in series to the R1 and the R2; and a switch SW2 connected, between the output terminal and the reference voltage, in series to the R3 and the R4, the SW1 and the SW2 controlling a connection between the output terminal and the reference voltage in response to a signal SW.
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