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Gate types
Functional principle of a complement gate

A NOT gate (English: NOT gate ), as a complement gates or inverters referred to, is a gate having an input and an output. It corresponds to the logical not . In propositional logic , the complement is represented by a ¬ in front of the corresponding symbols , in switching algebra by a cross.

The output delivers a 1 if a 0 is present at the input and a 0 if a 1 is present at the input. It therefore supplies the negation of the signal present at the input.


function Circuit symbol Truth table Relay logic
IEC 60617-12 US ANSI 91-1984 DIN 40700 (before 1976)

IEC NOT label.svg Not-gate-en.svg Logic-gate-inv-de.svg
A. Y
0 1
1 0
Relay not.svg

The non-character (¬) is at position 00AC in Unicode . Under Windows it can be entered by entering the number 0172 while holding down the Alt key ; under Linux with newer versions of X11 , it may by Compose, -, ,are generated.

Circuit symbols

The American and three European variants of the circuit symbol for the EMERGENCY gate (from left to right ANSI  91-1984, DIN  40900 old, DIN  40900 new,?)

There are several variants of the circuit symbol: The American is a triangle with a squiggle, the European either a rectangle with the inscription "1" or a semicircle with a squiggle or a black point at the entrance or exit.

Electronic realization

Simple execution of a non-gate with bipolar transistor in common emitter and collector resistor R C .
Non-gates in CMOS technology.

A non-gate can, for example, be based on a bipolar switching transistor in emitter circuit (see picture on the left), which connects the output to ground (logic 0) as soon as it is switched on. If it is off, the ground connection is interrupted and the output is at positive potential (logic 1) due to the collector resistance of the emitter circuit.

In integrated circuits , non-gates are usually implemented using the CMOS logic based on a p-channel and an n-channel MOSFET (see picture on the right).


Non-gates can be used as signal amplifiers (buffers). An integrated circuit with six inverters is, for example, the 74HC04 in high-speed CMOS technology. With inverters as the basic building blocks, tilt oscillators can also be implemented

In particular, inverters with a Schmitt trigger property can be connected upstream of the inputs of microcontrollers in order to generate clear logic signals from disturbed or constantly changing signals. One example is the 6-fold inverter circuit 40106.

NAND gates and NOR gates are common logic modules that negate each of their inputs, i.e. contain inverters there.


  • Ulrich Tietze, Christoph Schenk: Semiconductor circuit technology . 12th edition. Springer, 2002, ISBN 3-540-42849-6 .