| 摘要 |
PURPOSE:To accomplish an A/D converting operation for any kind of signal in a range close to the fullscale, by amplifying multiple kinds of analog signals varying in the range of change with different amplification factors to make the range of change thereof almost the same. CONSTITUTION:Output currents IX-IZ of light receiving elements 11-13 are converted into voltage signals with I/V conversion circuits 21-23. Here, when an I/V conversion resistance of the circuits 21-23 is represented by R1, output voltages thereof 21-23 are given by R1.IX, R1.IY and R1.IZ. These voltage signals are amplified with inversion amplification circuits 31-33 with amplification factors varying with signals and switched sequentially with a multiplexer 41 to be inputted into an A/D conversion circuit 42. The amplification factors of the circuits 31-33 are determined by an input resistance R2 and feedback resistances RX, RY and RZ respectively to obtain several voltage signals from the circuits 31-33 with the max. value thereof close to the max. convertible voltage Vmax of the circuit 42. This permits the performing of A/D conversion for any kind of signal with the circuit 42 in a range close to the fullscale.
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