Logic NAND / NOR Conversions

- using inverters to enable logic NAND / AND gates and NOR / OR gates to provide alternative functions

It often happens on a logic circuit board that an NAND gate and a few inverters may be available, whereas in reality an NOR function is required. If this occurs then all is not lost. It is still possible to create an OR function from an AND / NAND gate and inverters, or an AND gate from a NOR / OR function.

The diagram below gives some of the conversions. As an example it can be seen that a NOR gate is the same as an AND gate with two inverters on the input. It is then possible to add inverters to create the function that is required.

AND and OR Gate Equivalents

AND Gate and OR Gate Equivalents

These simple conversions can be used to save adding additional logic circuits into circuits. By using chips with spare gates, it is often possible to save adding additional chips, and thereby save cost and board space.

By Ian Poole

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