| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent a cutoff of low frequency signals while detecting an offset quickly. <P>SOLUTION: An offset detection circuit (22a, 22b, 24, 26) smooths an output of a variable gain amplifier 18 at a predetermined time constant to detect an offset, which is a DC component. The detected offset is added to an input to the variable gain amplifier by an addition circuit 28 to compensate the variable gain amplifier 18 for an output offset. The time constant in the offset detection circuit is changed by resistance values of variable resistances 22a, 22b. The time constant is changed to a small time constant when the gain of the variable gain amplifier 18 is changed, and later to a large time constant. <P>COPYRIGHT: (C)2012,JPO&INPIT |
