In which of the following gates, the output is 1, if and only if at least one input is 1?
A.
NOR
B.
AND
C.
OR
D.
NAND
Answer: Option C
Explanation:
In OR gate we need atleast one bit to be equal to 1 to generate the output as 1 because OR means any of the condition out of two is equal to 1 which means if atleast one input is 1 then it shows output as 1 . Number of 1's in input may be more than one but the output will always be 1 in OR gate. So the answer is 'C'
What is the minimum number of two-input NAND gates used to perform the function of two input OR gate ?
A.
one
B.
two
C.
three
D.
four
Answer: Option C
Explanation:
Y=A+B. This is the equation of OR gate. We require 3 NAND gates to create OR gate. We can also write
After 1st NAND operation Y = (A AND B)' Y= A' + B' (Demorgan's Law) After 2nd NAND operation Y= ( A' + B')' Y= A . B (Demorgan's Law) After 3rd NAND operation Y= ( A . B )' Y= A' + B ' (Demorgan's Law)