| 摘要 |
A problem that when signal input/output is conducted in an analogue signal format between two portions processing digital signals, the dynamic range becomes inadequate due to error variations of signal levels of an internal D/A converter and A/D converter is solved. In a gain setting, firstly the magnitude relation is so set that a minimum value in a signal level error variation range of a D/A converter ( 12 ) in a front stage DSP ( 1 ) is greater than a maximum value in a signal level error variation range of an A/D converter ( 21 ) in a rear stage signal processing block. Secondly, in a state that a signal having the level handled as a predetermined maximum value in the DSP ( 1 ) is inputted to a first GCA ( 13 ), the gain value of the first GCA ( 13 ) is so set that the level of a signal S 5 is the maximum in a range of below a prescribed value Vdr. Thirdly, the gain value of a second GCA ( 24 ) is so set that the level of the signal S 5 is the maximum in a range of equal or less than a prescribed value.
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