What is the minimum number of two-input NAND gates used to perform the…

2017

What is the minimum number of two-input NAND gates used to perform the function of two input OR gate, ISRO 2017

  1. A.

    One

  2. B.

    Two

  3. C.

    Three

  4. D.

    Four

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Correct answer: C

To implement a two-input OR gate using only NAND gates, apply De Morgan's laws. The expression A + B is equivalent to NOT(NOT(A) AND NOT(B)). This configuration requires three NAND gates: two used as inverters for the inputs and one to combine them. Therefore, the minimum number of NAND gates required is 3.

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