| 摘要 |
PROBLEM TO BE SOLVED: To evaluate device variance with high precision in a short period of time while eliminating the need for a program, a device, etc., for evaluating the device variance. SOLUTION: Counters 12 and 13 count signals A and B output from a pair of ring oscillators 9<SB>1</SB>and 10<SB>1</SB>, and a difference operation part 14 outputs the inversion signal of the signal B to a multiplier 16 when one of the counters enters a count-full state, and outputs the inversion signal of the signal A when the signal A is smaller than the signal B. The multiplier 16 squares and outputs an input operation result to an adder 17. The adder 17 adds a value stored in a flip-flop 19 to the operation result of the multiplier 16. The addition result is stored in the flip-flop 19. A similar process is performed for each pair of ring oscillators and a result is output as variance data. COPYRIGHT: (C)2011,JPO&INPIT
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