| 摘要 |
PURPOSE:To reduce the error of A/D conversion, by controlling the relative relation between the input range of each A/D converter and the DC level of a signal to be converted by inserting a reference signal into the ineffective period of the signal to be converted and detecting the level of the A/D converted output of the reference signal. CONSTITUTION:Analog switches 6 and 7 are controlled by horizontal blanking signals HBLK and a reference signal is inserted into the horizontal blanking period of an input signal. The reference signal is generated by a microcomputer 10 and D/A converter 8. At DC level adjusting sections 3 and 4 the DC level of the input signal is initialized so as to nearly satisfy the relation between the dynamic range of the input signal and the input ranges of A/D converters 1 and 2. The microcomputer 10 detects the deviation of a comparison reference level at the boundary between the input ranges of the A/D converters 1 and 2 by detecting the level distribution of the A/D converted output of the reference signal and reduces the deviation of the comparison reference level by controlling the DC level of the input signal.
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