A voltage on-off detector includes an inverter between a first voltage source and a first node and having an input terminal that receives a third voltage, a first transistor having a first gate, and a first source and a first drain between the first node and a second voltage source, a second transistor having a second source connected to the second voltage source, and a second gate and a second drain connected to the first node, and an amplifier having an input terminal connected to an output terminal of the inverter and configured to output a first voltage from the first voltage or a second voltage from the second voltage source based on or in response to an output of the inverter.