# What is a Logic Gate?

Malcolm Tatum

Logic gates are key components that are part of a digital circuit. Essentially, a logic gate helps to define a logical sequence of actions that take place under given circumstances. The typical logic gate will provide one output and two inputs as part of the logic sequence. In addition, the digital circuits will function at different voltage levels, using at least one of the two binary conditions in any given execution of a the sequence.

As of 2008, there are a total of seven different configurations for the logic gate. Each one is designed to handle various combinations and sequences of logical response that help the digital circuit to function at optimal efficiency. Because the logical command will vary according to circumstances, a digital circuit often employs several if not all of these seven configurations.

The AND gate is utilized when the two inputs and the outputs are ascertained to be similar. For example, if both inputs are judged to be positive, and the output is also determined to be positive, the AND protocol would be present. By contrast, the OR logical gate indicates that there is a difference between the inputs and the output that is at least different and most likely diametrically opposed.

The exclusive-OR gate is a logic gate that essentially functions in the same manner that an either/or comparison in linguistics works. With this type of logic pattern, the output may be positive while one but not both of the inputs was also positive. Unlike with the AND gate, all three elements do not have to be identical with an exclusive-OR gate, but at least one input must agree with the output.

The NOT gate essentially reverses the logic sequence, and is characterized by the usage of a single input rather than two. A NAND gate combines elements of both the AND gate and the NOT gate into a functionality that calls for a two tiered response that mimics the AND and then follows with the NOT logical sequence.

The NOR logic gate combines the processes associated with an OR gate and a NOT gate. Again working within a proscribed sequence, the output must be different from the two inputs. The two inputs will of necessity have to be the same.

The seventh type of logic gate is the XNOR gate. This approach combines the exclusive-OR gate with the NOR gate to come up with a logical sequence that judges the output to be positive if the inputs are both the same, but negative if the inputs differ.

All these examples of logic gate function come into play in carrying out various types of operations. While these seven examples are the generally defined profiles for a given logic gate, it is generally acknowledged that other logical sequences composed of other combinations of various aspects of the gates can and do take place. As technology continues to advance, the form and function of the logical gate concept will continue to expand, allowing for the performance of a wider range of tasks.

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