A bubble on the output of an AND gate makes the logic?

In digital electronics, the presence of a bubble on the output of a gate indicates inversion. For an AND gate, the standard operation is to output a high signal (1) only when all of its inputs are high. When a bubble is placed on the output, it signifies that the output is inverted. This modification transforms the AND operation into a NAND operation.

A NAND gate, therefore, will output a low signal (0) only when all its inputs are high, which is the opposite function of the AND gate. It effectively allows for a more versatile logic configuration, as NAND gates are universal gates, meaning any digital circuit can be constructed using only NAND gates.

This understanding clarifies why adding a bubble on the output of an AND gate results in NAND logic.