| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a variable gain inverting amplifier circuit capable of proper gain control at a low gain region, by suppressing influences due to parasitic capacitance around an input resistor to maintain gain linearity of the variable gain inverting amplifier circuit for a gain setting value according to a gain control signal. <P>SOLUTION: A variable gain inverting amplifier circuit controls a gain according to a ratio of an on-period in intermittence obtained by connecting and disconnecting a supply of an input signal Vin to an inverting input terminal of an arithmetic amplifier 20 by an on-off operation of a first switch 31. A point A connecting a side of an end of an input resistor 13 of the arithmetic amplifier 20 with a side of one pole of the first switch is connected to a ground point as a low impedance direct current voltage source via a second switch 32 of which on-off operation is controlled in the relation of a reverse phase to the on-off operation of the first switch 31, and a voltage follower circuit 34, to thereby suppress an influence of parasitic capacitance. <P>COPYRIGHT: (C)2013,JPO&INPIT |
