| 摘要 |
A frequency detecting circuit 10 detects frequency of a sampling pulse SP, and outputs the detected frequency as a detection value VOUT. A current adjusting circuit 20 adjusts a power supply current Ivd to be supplied to an AD converter 30 in accordance with the detection value VOUT. The power supply current Ivd varies continuously so as to follow the sampling frequency. As a result, an optimum power supply current Ivd can always be supplied in accordance with the operating frequency of the AD converter 30 . That is, power consumption of the AD converter 30 can be reduced. Since the power supply current Ivd can be adjusted in accordance with the sampling frequency, it is possible to form the AD converter 30 that has a wide frequency band and allows great versatility.
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