MadeEasy WorkBook: Digital Logic - Adder

Question

Comments

only A = 1 is sufficient.

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@subhanshu

output of first nand gate is 0 ( already given)

A=0 will never satisfy that because then output of first nand gate will be 1

so A=1 ...is that so ?

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Yes, because if we keep A = 0, then it will contradict the OP which is given 0 but we will get 1, So it is contradiction.

Answer 1

As they have fixed the o/p for 2 nand gates, it is not the correct implementation of the half adder. But given the diagram we can say the given combination satisfy the circuit requirement:

A-1 B-1 C-0 D-1

So option (D)