E7A07

PRACTICAL CIRCUITS · Digital circuits: digital circuit principles and logic circuits; classes of logic elements; positive and negative logic; frequency dividers; truth tables

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What logical operation does a NAND gate perform?

AIt produces a 0 at its output only if all inputs are 0
BIt produces a 1 at its output only if all inputs are 1
CIt produces a 0 at its output if some but not all inputs are 1
DIt produces a 0 at its output only if all inputs are 1

Why NAND is AND followed by NOT, so take the AND result and invert it. An AND gate outputs 1 only when every input is 1, so the NAND inverts that single case to 0 and outputs 1 for every other input combination. That makes the low output the unique, identifying state of a NAND gate.

Watch out The choice saying the output is 1 only when all inputs are 1 describes a plain AND gate, the un-inverted version; the choice about a 0 output only when all inputs are 0 describes an OR gate.

NAND = NOT-AND: all ones in, zero out. It is the only input pattern that pulls a NAND low.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

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