| 摘要 |
PURPOSE:To vary freely the gain of an A/D converter by inputting an analog input signal from a sensor after deciding a bias data for the share of one period so as to eliminate a bias component. CONSTITUTION:The bias data by one period is set to the 1st memory 3 at first. Then the input to a solid-state image pickup element is reduced to '0' and an analog input signal (a) being a sensor output is inputted to a non- inverting terminal of an analog subtractor 1. On the other hand, an analog data converted by a D/A converter 5 from the bias data stored in the memory 3 is inputted to an inverting terminal and the bias component data is subtracted from the signal (a). The result is converted into a digital signal by an A/D converter 2 and stored in the 2nd memory 7. The bias data in the memory 3 corresponding to the value stored in the memory 7 is corrected. Then the data in the memory 7 is zeroed entirely by repeating the operation above. The A/D converting value of the signal (a) eliminated from the bias component is obtained from the converter 2.
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