Experiment 20 - The 3-Input OR Gate

With the OR logic you can also combine 3 inputs. For this you can use OR gates which already contain 3 inputs...

You can easily fill up the truth table of the 3 input OR logic with the inputs A, B und C...

A B C Q 0 0 0 0 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 1 1 1 1 Truth Table of the 3-input OR logic.

Circuit symbol 3-input OR gate.

Circuit 3-input OR logic. (Enlarge)

With one of the three OR gates on the C-MOS IC 4075 you can set up the 3-input OR logic with the circuit shown.