Which type of logic device has an output that is opposite of the input?

The device that has an output that is opposite of the input is the inverter. An inverter, also known as a NOT gate, takes a single input signal and produces an output that is the logical negation of that input. For example, if the input is a high signal (1), the output will be a low signal (0), and vice versa. This fundamental operation of inverting the signal is central to digital logic design, allowing it to be used in a variety of applications, including signal conditioning and building complex logic circuits.

In contrast, other options like the AND and OR gates perform logical operations based on multiple inputs. The AND gate requires all its inputs to be high for the output to be high, while the OR gate requires at least one input to be high for the output to be high. The NAND gate combines the functionality of the AND gate with negation, producing a low output only when all its inputs are high, but it isn’t solely an inverter like the inverter is. Therefore, the unique and defining characteristic of the inverter is its ability to output the opposite of its input, making it the correct choice in this context.