| 摘要 |
Gain switching is performed by a DC amplifying circuit. The DC amplifying circuit is provided with individual gain generating circuits and a gain selecting circuit, and saturation preventing circuits are provided in earlier stages than the individual gain generating circuits. The individual gain generating circuit generates a gain G1, the individual gain generating circuit generates a gain G2 (where G2>G1), and the individual gain generating circuit generates a gain G3 (where G3>G2). The gain selecting circuit selects, as a used gain generating circuit, one of the individual gain generating circuits, and sends the output thereof to an A/D converting circuit in a later stage. A gain switching instruction is sent to the DC amplifying circuit, which controls the enabling/disabling of the saturation preventing operations of the saturation preventing circuits and the selecting operation for the gain selecting circuit, to prevent the occurrence of saturation in the individual gain generating circuits that generate higher gains than the gain generated by the used gain generating circuit.
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