Solution

Output of the first NAND gate: $X = \overline{A \cdot B}$
The second NAND gate has both inputs joined, so it works as a NOT gate: $Y = \overline{X \cdot X} = \overline{X}$
$Y = \overline{\overline{A \cdot B}} = A \cdot B$
So the circuit performs the logic function of an AND gate.

Concept NAND followed by NOT gives AND

Semiconductor Electronics: Materials, Devices and Simple Circuits in past papers

106 questions from this chapter have appeared across 24 exam years.