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OR gate

technology Maturity 11-13 Next article →

An OR gate is a very important part of digital tools.

OR ANSI Labelled
OR ANSI Labelled

It is a type of logic gate used in math. These gates help computers make decisions using bits. Bits are tiny bits of information that are either 1 or 0. You might also call these states true or false. They can also be called high or low. The OR gate is one of three basic parts. Together with AND and NOT gates, they can build any circuit.

OR from NAND
OR from NAND

This gate works by looking at its inputs to find a result. It uses a rule called logical disjunction. If any input is a 1, the output becomes a 1. The output is only a 0 if every input is 0. You can think of this like a plus sign. This is because the gate finds the maximum value between bits. It can have two inputs or even more inputs.

OR from NOR
OR from NOR

Some people call it an inclusive OR gate. This helps tell it apart from an exclusive OR gate. An exclusive OR gate is different when both inputs are 1.

Engineers use different symbols to draw these gates.

CMOS 4071 diagram
CMOS 4071 diagram

One symbol is the American or ANSI symbol. There is also a rectangular symbol from the IEC. The IEC symbol has a small mark that says "≥1". This mark means the output turns on with at least one active input. The old DIN symbol is no longer used today. Computers use these symbols to show how parts connect. These drawings help people build complex machines.

Many different chips contain these gates for use. One standard chip is the 4071 CMOS chip. This specific chip holds four separate OR gates inside. Another common device is the 7432 TTL device. There are many other versions of the 7432 chip too. Some versions like the 74HC32 use less power. The 74AC32 version is much faster at switching. There is even a 74LVC32 version for low voltage. Other chips like the 4075 have three inputs. The 4072 chip has two 4-input gates.

Sometimes, you might not have a standard OR gate. You can build one using other parts instead. You can use NAND or NOR gates to make an OR gate. This is a very helpful trick for builders. You can also make a "wired OR" by joining outputs together. This happens in certain types of transistor processes. It is a clever way to get the same result. Understanding these gates helps us understand how all technology works.

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🖼️ Images & Media (5)
File:CMOS 4071 diagram.svg
CMOS 4071 diagram.svg
File:OR ANSI Labelled.svg
OR ANSI Labelled.svg
File:OR from NAND.svg
OR from NAND.svg
File:OR from NOR.svg
OR from NOR.svg
File:Wired or.png
Wired or.png
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