| 摘要 |
A comparator is provided to enhance operation stability by outputting a stable voltage value during the reset period by adjusting the threshold voltage of a final stage. A comparator(117) includes first to third inverters(119a,119b,119c), a switch, and a capacitor. A reference voltage is supplied to the first inverter. The capacitor operates at an AC voltage. Input and output terminals of the first inverter are connected to the switch. The voltage from the output terminal of the first inverter is supplied to the input terminal of the first inverter. During a reset period, the output voltage from the first inverter serves as a threshold voltage for the first inverter. Threshold voltages of the first and second inverters are identical, while the terminal voltage of the third inverter is different from them. The threshold voltage, which has been outputted from the output terminal of the first inverter, is outputted from an output terminal of the second inverter via an input terminal of the second inverter. The threshold voltage from the output terminal of the second inverter is supplied to an input terminal of the third inverter.
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