| 摘要 |
It is an object of the present invention to enable a DC offset of a D/A converter to be removed substantially completely even when a DC offset exists in a comparator. An input switchover switch 160 is provided between complementary outputs A+, A- of a D/A converter 130 and an input of a comparator 150 . An input signal correction section 110 calculates a zero-cross delay value when an output A+ of the D/A converter 130 and a + input of the comparator 150 are connected and an output A- of the D/A converter 130 and a - input of the comparator 150 are connected, and a zero-cross delay value when the output A+ of the D/A converter 130 and the - input of the comparator 150 are connected and the output A- of the D/A converter 130 and the + input of the comparator 150 are connected, adds up the two zero-cross delay values calculated, decides whether the value is positive, negative or zero, integrates the result and uses a DC offset compensation value generated to thereby correct a digital input signal using an adder 128.
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