A three input NAND has two low inputs and a high input; the output will be

A three input NAND has two low inputs and a high input; the output will be

• A. High
• B. Low
• C. Undefined
• D. Tri-state

Answer: (A)

A NAND gate outputs the inverse of the AND of all its inputs. With three inputs, if any input is low, the AND of all inputs is 0. Here two inputs are low, so the AND result is 0, and inverting that gives a high output. The fact that one input is high doesn’t change this, because an AND requires all inputs to be high to produce 1. A standard NAND gate always provides a definite high or low for valid inputs, not a tri-state or undefined level. So the output is High.

A NAND gate outputs the inverse of the AND of all its inputs. With three inputs, if any input is low, the AND of all inputs is 0. Here two inputs are low, so the AND result is 0, and inverting that gives a high output. The fact that one input is high doesn’t change this, because an AND requires all inputs to be high to produce 1. A standard NAND gate always provides a definite high or low for valid inputs, not a tri-state or undefined level. So the output is High.