21. After partitioning, the number of vectors is given by
A. 2(m+n)
B. 2((m+n)/2)
C. 2n+ 2m
D. 22(m+n)
Answer: C
If the system is partitioned for testing, exhaustive testing can be reduced to 2n + 2m a much more reasonable proportion.
22. What are the dominant faults in diffusion layers?
A. short circuit faults
B. open circuit faults
C. short and open circuit faults
D. power supply faults
Answer: A
In MOS circuits, short circuits and open circuits in the metal layer and short circuits in the diffusion layer are the dominant faults experienced.
23. Test pattern generation is assisted using
A. automatic test pattern generator
B. exhaustive pattern generator
C. repeated pattern generator
D. loop pattern generator
Answer: A
Test pattern generation is assisted using automatic test pattern generators but they are complicated to use properly and ATPG costs tend to rise rapidly with circuit size.
24. _____ of faults are easier to detect.
A. 50%
B. 60%
C. 70%
D. 80%
Answer: D
It is relatively easy to detect the first 80% of faults using various classical test strategies.
25. Hot carrier injection causes
A. threshold voltage shift
B. transconductance degradation
C. threshold voltage shift & transconductance degradation
D. none of the mentioned
Answer: C
Hot carrier injection causes both threshold voltage shift and transconductance degradation due to charge accumulation in the gate oxide.
26. Oxide breakdown occurs due to
A. electrostatic charge
B. threshold voltage
C. voltage shift
D. poor input/output pad circuitry
Answer: D
Oxide breakdown occurs due to inadequate protection against electrostatic discharge and also due to defects or poor design in input/output pad circuitry.
27. Which model is used for pc board testing?
A. stuck at
B. stuck in
C. stuck on
D. stuck through
Answer: A
The stuck-at model is used in the testing of pc boards and is not sufficient to test actual VLSI CMOS circuits.
28. The input signal combination in exhaustive testing is given as
A. 2N
B. 21/N
C. 2(M+N)
D. 1/2N
Answer: A
For testing an N input circuit using exhaustive testing, the total number of input combinations can be given as 2N.
29. Observability is the process of
A. checking all inputs
B. checking all outputs
C. checking all possible inputs
D. checking errors and performance
Answer: B
Observability is the process of observing outputs for all the input combinations.
30. Exhaustive testing is suitable when N is
A. small
B. large
C. any value for N
D. very large
Answer: A
Exhaustive testing is the process where all possible input combinations are used. This is suitable when N is relatively small.
