To stably obtain an output even when a power source has a value close to the threshold of a voltage decision circuit by providing a Schmitt circuit which stably outputs a decision signal corresponding to the value of the output of a decision circuit.
In a voltage decision circuit 5, the voltage of a 2nd unit 53 drops as the voltage of a power source 10 drops. Then when the voltage of the 2nd unit 53 drops below the threshold of a 1st inverter 541, the 1st inverter 541 outputs a signal of source voltage level and a 3rd inverter 543 inputting it outputs a signal of ground level. The 3rd unit 54 is composed of a Schmitt circuit, so its on/off characteristics show hysteresis. Therefore, even when the output 534 of the 2nd unit 53 has a value close to the threshold of the 1st inverter, the 1st inverter 541 does not turns on and off frequently and a stable output 51 can be obtained.
KOURA MASATO
HONGO KATSUNOBU
