| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that in a subtraction circuit of a pickup device by a conventional technology, since subtraction processing is performed after respective current signals are converted to voltage signals, a first current voltage converter 7 and a second current voltage converter are required, respectively, in order to voltage-convert a first photoelectric current Ip1 and a second photoelectric current IP2, respectively, and a layout area required for the subtraction circuit is large. SOLUTION: In this subtraction circuit of the pickup device, the first photoelectric current IP1 is inputted to a connection point P1 of a non-inversion input terminal of an operation amplifier 3 and a first resistor R1, and the second photoelectric current IP2 is inputted to a connection point P2 of the inversion input terminal and the second resistor R2. Reference voltages Vref are applied to the first resistor R1 and the second resistor R2. In this case, potential differences corresponding to the first photoelectric current IP1 and the second photoelectric current IP2 are caused in the first resistor R1 and the second resistor R2. COPYRIGHT: (C)2008,JPO&INPIT
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