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 
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'. Click on Discuss to view users comments. 
A.  Rise time 
B.  Decay time 
C.  Propagation time 
D.  Charging time 
Option: C Explanation : Click on Discuss to view users comments. aruna said: (2:13am on Sunday 8th September 2013)
propagation time

A.  Rise time 
B.  Decay time 
C.  Propagation time 
D.  Operating speed 
Option: A Explanation : Click on Discuss to view users comments. 
A.  Operating speed 
B.  Propagation speed 
C.  Binary level transaction period 
D.  Charging time 
Option: A Explanation : Click on Discuss to view users comments. 
What is the minimum number of twoinput NAND gates used to perform the function of two input OR gate ?
A.  one 
B.  two 
C.  three 
D.  four 
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 1^{st} NAND operation So we need 3 NAND gates. Click on Discuss to view users comments. meena vinay said: (3:45pm on Tuesday 21st April 2015)
the ouput after ist NAND and third NAND is same.So the answer is not correct
Gitanjali said: (3:43pm on Saturday 26th November 2016)
After first nand gate as well we are getting or answer .So the answer shd be after one nand gate
prathap said: (12:12am on Thursday 22nd December 2016)
when we see the implementation of OR gate using NAND gate it is clearly saying that the minimum number of 2 input required are 3.
Shahroze Arslan said: (8:35am on Wednesday 9th May 2018)
a simple way to check this is through truth tableThe truth table of one OR gate (accepting two inputs minimum) and one NAND (accepting two inputs minimum) is same

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