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