Method and an apparatus for measuring the input threshold level of device under test

1. A method for measuring a input threshold level of a device under test which comprises:

inputting a first signal that includes a first slope and a second slope having different gradients and a known relative temporal position relationship to the device under test;

measuring a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said first slope and a time when a logic level transition occurs in a output signal of said device under test in response to said second slope; and

calculating said input threshold level by using at least the gradients of said slopes and said time interval.

2. The method of claim 1 , wherein said first slope is a rising slope; said second slope is a falling slope; and said first slope and said second slope are at least one part of the same triangle wave or the same trapezoid wave.

3. The method of claim 1 , wherein the maximum level of said first slope equals the maximum level of said second slope; and the minimum level of said first slope equals the minimum level of said second slope.

4. A method for measuring a input threshold level of a device under test which comprises:

inputting a first signal including a first slope and a second slope having different gradients and a known relative temporal position relationship to the device under test;

inputting a second signal including a third slope and a fourth slope having different gradients and a known relative temporal position relationship to the device under test;

measuring a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said first slope and a time when a logic level transition occurs in a output signal of said device under test in response to said second slope;

measuring a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said third slope and a time when a logic level transition occurs in a output signal of said device under test in response to said fourth slope; and

calculating said input threshold level by using at least the gradients of said slopes and said time intervals.

5. The method of claim 4 , wherein said first slope is a rising slope; said second slope is a falling slope; and said first slope and said second slope are at least one part of the same triangle wave or the same trapezoid wave.

6. The method according to claim 4 , wherein said first slope and said third slope are rising slopes; said second slope and said fourth slope are falling slopes; said first slope and said second slope are at least a part of the same triangle wave or the same trapezoid wave; and said third slope and said fourth slope are at least one part of the same triangle wave or the same trapezoid wave.

7. The method according to claim 4 , wherein the maximum level of said first slope equals the maximum level of said second slope; and the minimum level of said first slope equals the minimum level of said second slope.

8. The method according to claim 4 , wherein the maximum level of said first slope equals the maximum level of said second slope, the minimum level of said first slope equals the minimum level of said second slope, the maximum level of said third slope equals the maximum level of said fourth slope, and the minimum level of said third slope equals the minimum level of said fourth slope.

9. A method for measuring a input threshold level of the device under test which comprises:

inputting a signal having a first slope and a second slope having different gradients and a known relative temporal position relationship, and a third slope and a fourth slope having different gradients and a known relative temporal position relationship to the device under test;

measuring a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said first slope and a time when a logic level transition occurs in a output signal of said device under test in response to said second slope;

measuring a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said third slope and a time when a logic level transition occurs in a output signal of said device under test in response to said fourth slope; and

calculating said input threshold level by using at least the gradients of said slopes and said time intervals.

10. The method of claim 9 , wherein said first slope is a rising slope;

said second slope is a falling slope; and said first slope and said second slope are at least one part of the same triangle wave or the same trapezoid wave.

11. The method according to claim 9 , wherein

said first slope and said third slope are rising slopes;

said second slope and said fourth slope are falling slopes;

said first slope and said second slope are at least a part of the same triangle wave or the same trapezoid wave; and

said third slope and said fourth slope are at least one part of the same triangle wave or the same trapezoid wave.

12. The method according to claim 9 , wherein the maximum level of said first slope equals the maximum level of said second slope; and the minimum level of said first slope equals the minimum level of said second slope.

13. The method according to claim 9 , wherein the maximum level of said first slope equals the maximum level of said second slope, the minimum level of said first slope equals the minimum level of said second slope, the maximum level of said third slope equals the maximum level of said fourth slope, and the minimum level of said third slope equals the minimum level of said fourth slope.

14. An apparatus for measuring a input threshold level of a device under test which comprises:

a signal generator that generates a first signal that comprises a first slope and a second slope having different gradients and a known relative temporal position relationship;

a time measuring device that measures a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said first slope and a time when a logic level transition occurs in a output signal of said device under test in response to said second slope; and

a calculator that calculates said input threshold level by using at least the gradients of said slopes and said time interval.

15. The apparatus according to claim 14 , wherein said first slope is a rising slope; said second slope is a falling slope; and said first slope and said second slope are at least a part of the same triangle wave or the same trapezoid wave.

16. The apparatus of claim 14 , wherein the maximum level of said first slope equals the maximum level of said second slope, and the minimum level of said first slope equals the minimum level of said second slope.

17. An apparatus for measuring a input threshold level of a device under test which comprises:

a first signal generator that generates a first signal that includes a first slope and a second slope having different gradients and a known relative temporal position relationship;

a second signal generator that generates a second signal that includes a third slope and a fourth slope having different gradients and a known relative temporal position relationship;

a first time measuring device that measures a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said first slope and a time when a logic level transition occurs in a output signal of said device under test in response to said second slope;

a second time measuring device that measures a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said third slope and a time when a logic level transition occurs in a output signal of said device under test in response to said fourth slope; and

a calculator that calculates said input threshold level by using at least the gradients of said slopes and said time intervals.

18. The apparatus according to claim 17 , wherein said first slope is a rising slope; said second slope is a falling slope; and said first slope and said second slope are at least a part of the same triangle wave or the same trapezoid wave.

19. The apparatus of claim 17 , wherein said first slope and said third slope are rising slopes; said second slope and said fourth slope are falling slopes; said first slope and said second slope are at least one part of the same triangle wave or the same trapezoid wave; and said third slope and said fourth slope are at least one part of the same triangle wave or the same trapezoid wave.

20. The apparatus of claim 17 , wherein the maximum level of said first slope equals the maximum level of said second slope, and the minimum level of said first slope equals the minimum level of said second slope.

21. The apparatus of claim 17 , wherein the maximum level of said first slope equals the maximum level of said second slope, the minimum level of said first slope equals the minimum level of said second slope, the maximum level of said third slope equals the maximum level of said fourth slope, and the minimum level of said third slope equals the minimum level of said fourth slope.

22. An apparatus for measuring a input threshold level of a device under test which comprises:

a signal generator that generates a signal that includes a first slope and a second slope having different gradients and a known relative temporal position relationship, and a third slope and a fourth slope having different gradients and a known relative temporal position relationship;

a first time measuring device that measures a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said first slope and a time when a logic level transition occurs in a output signal of said device under test in response to said second slope;

a second time measuring device that measures a time interval between a time when a logic level transition occurs in a output signal of said device under test in response to said third slope and a time when a logic level transition occurs in a output signal of said device under test in response to said fourth slope; and

a calculator that calculates said input threshold level by using at least the gradients of said slopes and said time intervals.

23. The apparatus according to claim 22 , wherein said first slope is a rising slope; said second slope is a falling slope; and said first slope and said second slope are at least a part of the same triangle wave or the same trapezoid wave.

24. The apparatus of claim 22 , wherein said first slope and said third slope are rising slopes; said second slope and said fourth slope are falling slopes; said first slope and said second slope are at least one part of the same triangle wave or the same trapezoid wave; and said third slope and said fourth slope are at least one part of the same triangle wave or the same trapezoid wave.

25. The apparatus of claim 22 , wherein the maximum level of said first slope equals the maximum level of said second slope, and the minimum level of said first slope equals the minimum level of said second slope.

26. The apparatus of claim 22 , wherein the maximum level of said first slope equals the maximum level of said second slope, the minimum level of said first slope equals the minimum level of said second slope, the maximum level of said third slope equals the maximum level of said fourth slope, and the minimum level of said third slope equals the minimum level of said fourth slope.