LOGICAL DEVICE TESTER AND TESTING METHOD

PROBLEM TO BE SOLVED: To set a state where the level of a supply voltage or an input voltage can be varied depending on the noise arbitrarily by synthesizing a specified voltage and a test noise to produce a signal being delivered, as a test voltage, to a voltage input terminal. SOLUTION: An input voltage supply section 10 generates a specified power supply voltage or input voltage having an amplitude and a frequency being set arbitrarily which is then delivered to a signal synthesizing section 14. The signal synthesizing section 14 synthesizes the specified power supply voltage or input voltage received at an input terminal IN1 from the input voltage supply section 10 and a test noise received at an input terminal IN2 from a noise supply section 12. The signal synthesizing section 14 delivers a synthesized signal, as a test power supply voltage or a test input voltage, to the power supply voltage input terminal or the input terminal through an output terminal OUT. The logical device operates in response to the test power supply voltage or executes an inherent function in response to the test input voltage.