The logic gates in which all the inputs must be low to get a high output are

The logic gates in which all the inputs must be low to get a high output are
  1. NAND and AND
  2. NOR and NAND
  3. OR and AND
  4. AND and NOR

Solution

Truth table for AND, OR, NAND and NOR gate for two input $A$ and $B$ are given below. AND gate \begin{array}{|ccc|} \hlineA & B & Output Y=A B \\ \hline 0 & 0 & 0 \\ \hline 0 & 1 & 0 \\ \hline 1 & 0 & 0 \\ \hline 1 & 1 & 1 \\ \hline \end{array} OR gate \begin{array}{|llc|} \hlineA & B & Output Y=A+B \\ \hline 0 & 0 & 0 \\ \hline 0 & 1 & 1 \\ \hline 1 & 0 & 1 \\ \hline 1 & 1 & 1 \\ \hline \end{array} NOR gate \begin{array}{|cccc|} \hlineA & B & A+B & Output Y=\bar{A}+\bar{B} \\ \hline 0 & 0 & 0 & 1 \\ \hline 0 & 1 & 1 & 0 \\ \hline 1 & 0 & 1 & 0 \\ \hline 1 & 1 & 0 & 0 \\ \hline \end{array} NAND gate \begin{array}{|rrrc|} \hlineA & B & A+B & Output Y=\overline{A B} \\ \hline 0 & 0 & 0 & 1 \\ \hline 0 & 1 & 0 & 1 \\ \hline 1 & 0 & 0 & 1 \\ \hline 1 & 1 & 1 & 0 \\ \hline \end{array} From above truth tables, it is clear that in NOR and NAND gate, if all the inputs are low, then their outputs are high.

Asked in: AP EAMCET 2022 (06 Jul Shift 2)

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