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