| 摘要 |
PROBLEM TO BE SOLVED: To hold frequency characteristics and DC characteristics constant irrelevantly to a variation in gain, in a gain control amplifier whose gain can be switched. SOLUTION: A voltage feedback type operational amplifier 10 is used as a main amplification part. A constitution composed of a combination of resistance elements 22 to 28 and switches S24 to S28 is employed as a gain control circuit 20 connected to an inverted input terminal (-) of the operational amplifier 10. Two-input/one-output type switches are used as the switches S24 to S28, an input signal Vi inputted to one input terminal of each switch and the other input terminal connected to the ground (GND) as potential connected to an uninverted input terminal (+) of the operational amplifier 10. Output terminals of the respective switches S24 to S28 are connected to corresponding resistance elements 24 to 28 for gain-switching. A feedback quantity is held constant irrelevantly to the of the switches to keep frequency characteristics and DC characteristics constant irrelevantly to a variation in gain. COPYRIGHT: (C)2006,JPO&NCIPI
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