Simple Logic Gates

First, let’s clarify some key terms.

Gate is a device that performs a basic operation on electrical signals, accepting one or more input signals and producing a single output signal. Circuit is a combination of interacting gates designed to accomplish a specific logical function.

There are three ways to represent each logic gate. Boolean algebra is a mathematical notation. Logic diagram is a graphical representation of a circuit. Truth table is a table showing all possible input values and their associated outputs.

The input signals for all simple logic gate are 0 and 1.

NOT Gate: Invert

Outputs have an opposite symbol with inputs.

Example: Microwave oven will off(0) when the door is opened(1).

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And Gate: All

When all inputs are on, then the result will be on.

Example: The fire alarm will turn on(1) if there is smoke(1) and the temperature increase suddenly(1).

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NAND Gate

When all inputs are on, then the result will be off. NAND gate is opposite to AND gate.

Example: The advanced security door will unlock(0) when the passport is correct(1) and the finger print is correct. 

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OR Gate: At Least One

When at least one input is 1(on), the result will be on.

Example: The lock of the door of a apartment will release(0) as long as either the passport is correct(1) or the user scans the room card(1).

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NOR Gate

NOR gate is opposite to OR gate.

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XOR Gate: Only one

XOR stands for exclusive OR gate. When only one input is on, the result will be on.

Example: There are two switches of light in a room. Originally, they are turned down(0), I turn on switch A(1) while switch B is off(0), the light will be on(1). When I turn on switch B(1) while switch A is still on(1), the light will be off(0).

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Gates with More Inputs

What is the result for each case when we are using Three-input AND Gate?

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Work Cited

Dale, Nell and John Lewis. Computer Science Illuminated. Print.

Kyaw, Pyae Sone. “Simple Logic Gates”. 2016. Presentation.