The NOR logic gate is an important electronic component that performs a logical OR operation, followed by a logical NOT operation. It is used in digital logic circuits to produce a result that is the opposite of that of the logical OR operation. It is one of the three basic logic gates, the others being the NOT, or inverter, gate and the AND gate.
The word “NOR” is an acronym for the phrase “NOT OR,” which is the inverted form of the binary operator OR. It is commonly used to produce a logical low output level from two inputs of the same logic level. For example, if both inputs are at logic level low, the output is also low. In this way, NOR gates are commonly used on circuit boards to prevent input signals from interfering with each other.
The NOR gate is a universal gate, meaning that any other logical function can be implemented using a collection of NOR gates. This makes it a versatile component in digital logic circuits. Additionally, NOR gates are easily implemented in hardware, since all transistors that are needed to make it are N-type. The symbol of a NOR gate in a circuit layout is typically a filled diamond as can be seen in the illustration.
The NOR gate acts as a logic function when provided with two binary inputs and produces an output which is the inverse of the OR function. In Boolean notation, it is expressed as
A+B = Q
where Q is the output, A and B are binary inputs and the “+” sign stands for logical OR.
The output of a NOR gate is false when either or both inputs are true. This makes it exactly opposite of an AND gate which produces an output true only when both inputs are true. This type of gate can be used in applications such as alarm systems, logic controllers, and computers.
