A power-supply circuit includes a capacitor, which is connected to a terminal at a first end while being grounded at the second end, for supplying a hold voltage between both ends thereof to a load; a capacitor connected, via a diode, to the terminal at a first end; an operational amplifier for raising a voltage at the second end of the capacitor, in response to a reduction in the hold voltage, such that the hold voltage becomes equal to a target voltage; and a transistor.
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