UGC NET CS 2007 June-Paper-2

Question 7

Which of the following expression remove hazard form : xy+zx’ ?

A	xy+zx’
B	xy+zx’
C	xy+zx’+yz
D	xy+zx’+wz

Digital-Logic-DesignCircuits-Output

Question 7 Explanation:

→ A static hazard occurs if a circuit produces incorrect output value momentarily before stabilizing to its correct value.
→ Generally Hazard occurs due to different delays in different paths of the circuit.
→ In the expression xy +zx’ the variable x is in true form in one term(xy) and in complement in other term(zx’).
→ Delay occurs due to the presence of NOT gate.
If input xyz=111 then output is 1.
If input xyz=011 then output stays momentarily in state 0 then settles in state 1.
→ Adding the term yz(select y from xy and z from zx’) eliminates the hazard.

Correct Answer: C

Question 7 Explanation:

→ A static hazard occurs if a circuit produces incorrect output value momentarily before stabilizing to its correct value.
→ Generally Hazard occurs due to different delays in different paths of the circuit.
→ In the expression xy +zx’ the variable x is in true form in one term(xy) and in complement in other term(zx’).
→ Delay occurs due to the presence of NOT gate.
If input xyz=111 then output is 1.
If input xyz=011 then output stays momentarily in state 0 then settles in state 1.
→ Adding the term yz(select y from xy and z from zx’) eliminates the hazard.