The logical operation of the following circuit is

The circuit consists of three NAND gates. The first two gates have their inputs tied together, acting as NOT gates that produce A' and B'. The final gate is a NAND gate taking these inverted signals as inputs, yielding the output expression Y = (A' * B')'. By applying De Morgan's laws, this simplifies to Y = A + B, which is the standard Boolean expression for an OR gate.