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Inverter (logic gate)

technology Maturity 11-13 Next article →

An inverter is a tiny but vital tool in digital logic. It is also known as a NOT gate.

Not-gate-en
Not-gate-en

This tool is very important for computers. It performs a job called logical negation. This means it takes an input and gives the opposite result. In computer math, we use bits to send information. These bits are usually represented as a one or a zero. An inverter is one of three basic gates used to build circuits. You can use these three gates to build any math circuit you want.

How does an inverter work? It works by flipping the signal it receives. If you put a one into the gate, it outputs a zero. If you put a zero in, it outputs a one.

NOT from NAND
NOT from NAND

People sometimes call this action "flipping" the bits. You might also hear people use words like high and low. This happens because the gate changes the voltage levels. A low voltage input becomes a high voltage output. A high voltage input becomes a low voltage output. It is a very simple and direct way to change a signal.

Engineers use different parts to build these inverters. One way uses a single NMOS transistor. Another way uses a single PMOS transistor with a resistor. This can be made at a low cost. However, it uses more power and is slower.

CMOS 4049 diagram
CMOS 4049 diagram

A better way is the CMOS configuration. This uses two complementary transistors together. In this setup, one transistor is always turned off. This helps the device use much less power. It also makes the processing speed much faster.

There are many specific parts that hold these gates. For example, the 7404 TTL chip has 14 pins. The 4049 CMOS chip is a bit larger with 16 pins. This chip is called a hex inverter. The word "hex" means it contains six inverters inside.

CMOS 4049 diagram
CMOS 4049 diagram

Out of those 16 pins, two are for power. The other 12 pins are for the inputs and outputs. This allows one small chip to do many jobs at once. These chips are building blocks for much bigger machines.

Scientists use a special graph to check an inverter. This graph is called a voltage transfer curve.

Inverter voltage transfer curve
Inverter voltage transfer curve

It shows the relationship between the input and output voltage. A good inverter should switch very quickly. This means the slope on the graph should be very steep. A steep slope shows precise switching between on and off. Engineers also use this graph to measure noise tolerance. This helps them see if the signal stays clear. It is a key way to measure how well a gate works.

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🖼️ Images & Media (6)
File:Not-gate-en.svg
Not-gate-en.svg
File:CMOS 4049 diagram.svg
CMOS 4049 diagram.svg
File:NOT ANSI Labelled.svg
NOT ANSI Labelled.svg
File:NOT from NAND.svg
NOT from NAND.svg
File:NOT from NOR.svg
NOT from NOR.svg
File:Inverter voltage transfer curve.png
Inverter voltage transfer curve.png
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