| 摘要 |
PROBLEM TO BE SOLVED: To control the transconductance of each of transconductance amplifiers which construct an analog filter with high accuracy and also to control the filter characteristic with high accuracy. SOLUTION: A transconductance control circuit 19 consists of a replica transconductance amplifier 21 which has the same characteristic as each of transconductance amplifiers constructing an analog filter 10, a resistor 22, the reference voltage sources 20 and 25 to 28, a selector 44, a differential amplifier 24 and a voltage/current converter 29. A switch 42 of the selector 44 can be connected to the sources 25 to 28 in every fixed cycle by means of a clock 41. A switch 43 of a selector 40 can be connected to the capacities 35 to 38 in every fixed cycle by means of the clock 41.
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