| 摘要 |
PROBLEM TO BE SOLVED: To allow a comparison reference value to be set over supply voltage by including a diode connected to an input terminal, two resistors connected in series from the diode to a power source and a means for detecting voltage at their common connection point. SOLUTION: When voltage Vin of an input terminal 1>= supply voltage (Vdd ), a diode D is cut off so that voltage at an output terminal 2 is 'L'. When the voltage Vin drops to a negative value less than 0V, and resistors are set so that R1>R2 and voltage at a node N1 is positive while it is higher than a threshold value of an inverter INV1, lower limit reference voltage (Vβ) can be set to negative voltage. At this time, when the input voltage Vin is Vin <=Vβvoltage at the output terminal 2 is 'H', while when Vin <Vβvoltage at the output terminal 2 is 'L'. Thus it is possible to detect whether V. >Vβor not, and the reference voltage Vβcan be set at Vβ<0.
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