| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a feedback control circuit which is tolerant of noise by suppressing influence of noise even when the noise is given to the output of an integrating circuit or low-pass filter. <P>SOLUTION: The output amplitude of a variable gain amplifier 10 is compared with the target value of a differential amplifier 12. When the amplitude is smaller than the target value, the gain of the variable gain amplifier 10 increases and the output amplitude becomes large. When the amplitude is larger than the target value, the gain of the variable gain amplifier 10 decreases and the output amplitude becomes small. This feedback control circuit is provided with an input switch 14 which inverts the output polarity of the differential amplifier 12, an input switch 15 which inverts the output polarity of a differential amplifier 13, comparators 16 and 17, an IDAC 19, and a logic circuit 18 which turns on and off the input switches 14 and 15 and controls the output current value of the IDAC 19, and only a portion of the gain variation range of the variable gain amplifier 10 is made to correspond to the potential of VLP. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
