There are many applications where it is desirable to have both noninverted and inverted outputs.
Examples include a single-input gate that is both an inverter and a noninverting buffer, or a two-input logic gate that is both an AND and a NAND. Such gates are called complementary output gates and are particularly useful in circuits where PCB space is at a premium. These are also useful in circuits where the addition of an inverter to obtain the inverted output introduces an undesirable time delay between inverted and noninverted outputs. shows the circuit symbols of complementary buffer, AND, OR and EX-OR gates.