# Digital Electronics - Logic Gates - Discussion

### Discussion :: Logic Gates - General Questions (Q.No.2)

2.

If a 3-input NOR gate has eight input possibilities, how many of those possibilities will result in a HIGH output?

 [A]. 1 [B]. 2 [C]. 7 [D]. 8

Explanation:

No answer description available for this question.

 Tribhuwan said: (Dec 27, 2010) The output of a NOR gate is high only when all the input will be in low (0) state

 Bhavani said: (Dec 31, 2010) Correct.

 Rajeev Kumer said: (Feb 14, 2011) Hi, can you explain it clearly?

 Rajesh said: (Feb 23, 2011) I want to know how the ans is A.

 Anju said: (Mar 13, 2011) When A=0, B=0, C=0 then OR gate output is LOW then NOR gate output is HIGH.

 Madhu said: (Jul 25, 2011) What about 3 inputs. 8 inputs? I cant understand.

 Rashmi said: (Jul 28, 2011) Truth table of NOR ```i/pa i/pb o/p 0 0 1 0 1 0 1 0 0 1 1 0``` Now in 8 connection only 1 can have 0 0 0 i/p so that 1 connectn can remain high.

 Baljeet Kaur said: (Oct 1, 2011) NOR gate have two or more i/p and only one o/p , AND gate have also two or more i/p and one o/p and NOT gate have 2 i/p or 1 o/p.

 Arvind Kumar said: (Nov 29, 2011) In NOR gate it complement of sum of input signal so high output is 1.

 Dipasree said: (Dec 26, 2011) But it is a 3 input nor gate not 2 input.

 Dipasree Banerjee said: (Dec 26, 2011) The answer is A B C Y 0 0 0 0 0 0 1 1 * * * 1 * * * 1 SO

 Rashmi said: (Jan 16, 2012) For nor gate the basic truth table s A B Y 0 0 1 0 1 0 1 0 0 1 1 0 and in the same way truth tablefor 3input norgate s A B C Y 0 0 0 1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 0 here only one output s high.hence option A

 Devendra Babu said: (Mar 19, 2012) Actually the truth table for NOR Gate is given by A B Y 0 0 1 0 1 0 1 0 0 1 1 0 and similarly truth table for 3input nor gate s A B C Y 0 0 0 1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 0 So, only one output s high.hence option A is the correct option to be elected which was given in the choices

 Js Dhaker said: (Mar 28, 2012) A B C = OR NOR 0 0 0 0 1 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 0

 Al-Imran Masum said: (May 28, 2012) Only, . A=0, B=0, C=0 is equal output is 1. That means high. But the another possibilities output is also 0. That means low. So our answer is 1.

 Kajal Ahuja said: (Jun 30, 2012) The output of NOR gate is high only when all the inputs given to the gate are low that means the output will be 1 only when all inputs are 0.

 Heena said: (Aug 3, 2012) When both the inputs of OR gate are high then also output of NOR gate is high. So we cannot say that only in case of both low it will be high.

 Veeru said: (Aug 19, 2012) NOR means compliment of or for a 3 input or gate it has 7 possibilities of high. Hence the ans is 1

 Aarti said: (Sep 22, 2012) NOR is OR+INVERT so OR will be 1 when any one of inputs is '1' but in NOR output will be inverted OR. So when all inputs are '0' OR output will be '0' and its inverted means NOR output will be '1'.

 Nandi said: (Nov 15, 2012) But do we have more than 2 input NOR gate?

 Janci said: (Jan 2, 2014) Yes @Nandi 4078b is the single 8 inputs norgate in CMOS technology.

 Hhki said: (Oct 8, 2015) NOR gate consider the outputs to be high if the inversion of it is high.

 Megu said: (Aug 13, 2016) Above all are false.

 Sangeetha said: (Sep 30, 2016) If all input is 1 then it is high, if all inputs are zero then it is low.

 Punju said: (Dec 9, 2016) By the truth table at 0 0 input output is 1 and remaining all are 0. Therefore the high output is the 1. Therefore, the ans is option : A.

 Pooooja said: (Jan 5, 2017) Yeah, right thanks @Punju.

 Hariom Sharma said: (Jan 14, 2017) i/p- 000 then o/p- 111 (high).

 Anoop K Sivan said: (Feb 20, 2017) Just add all three inputs and NOT it for the actual o/p.

 James said: (Mar 20, 2017) I have a question. Prove this for me AB+(barB)C+AB = AB+(barB)C.

 Ashutosh Jaiswal said: (Sep 29, 2017) Actually the truth table for NOR Gate is given by A B Y 0 0 1 0 1 0 1 0 0 1 1 0 And similarly truth table for 3input nor gate is; A B C Y 0 0 0 1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 0 So, only one output is high. Hence option A is the correct option to be elected which was given in the choices.

 Vijaya said: (Dec 12, 2018) Thank you all.

 Avadhesh Kumar Soni said: (Oct 9, 2019) NOR gate will only produce a logic 1 output when all inputs are simultaneously at logic 0. Any other input combination will produce a logic 0 output.

 Nitin Gawande said: (Feb 24, 2020) In nor gate if any input is the high answer will be 0.

 Shivam said: (Jun 1, 2020) Because in nor gate if any of the input is high the output is low. So, we are left with only one case when output is high i.e. A=0, B=0 and C=0.

 Muhammad Shaigan said: (Jul 15, 2020) I am not getting. Can anyone explain this? please.