The NOT gate, also known as an inverter, is a logic gate that performs logical negation on its input. It is basically a switch that changes the state of the given input from 0 (low) to 1 (high). The output of the NOT gate is opposite to the input; a low input yields a high output and a high input yields a low output.
A NOT gate with a single input is technically termed a ‘one-input inverter’. They are usually seen in the form of an ‘integrated inverter gate’ which consists of several gates in a single package for the purpose of cost-saving. An integrated inverter gate may consist of NAND or NOR gates or the combination of both.
The most common logic symbols for the NOT gate are exclamation mark (!) and circle with a small arrow (O) signifying the inverse effect of the gate.
A NOT gate is a fundamental building block in modern digital technology and can be used for a wide variety of purposes. Some of the most common applications are incombinational logic, controlling clock kicks, basic Memory Cell design, as a Building Block in Flip-flops or Multi-Level logic, and in Control Circuits.
The NOT gate operation can be summarized in one simple sentence: it changes the state of its input, be it 0 or 1 (low or high) into a single output of the opposite state.
In digital circuits, OR and AND gates are typically used to transform a number of individual bits into a single output but a NOT gate can usually be used to transform a single bit into an output bit that satisfies the needs of the particular application. Thus, NOT gate can be used to complement single-bit operations like in multi-level logic or in flip-flops to ensure proper operation.
NOT gates are most commonly implemented using Field Effect Transistors (FETs) such as the MOSFET, or Metal Oxide Semiconductor (MOS) transistor. The FET input is localized onto the gate terminal and the output is found at the drain terminal, while the source terminal is connected to the ground terminal during the operation.
