Logic Circuits

Dividing Line


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When different Logic Gates are connected they form a Logic Circuit.  Logic Circuits are designed to perform a particular function.

Logic Circuit


Information

Creating Truth Table for a Logic Circuit is a little more complicated than creating one for a simple Logic Gate ...

Add letters for the inputs to the circuit.

Logic Circuit


Label the output of each Logic Gate.  This gives you the columns for your Truth Table.

Logic Circuit


Create the Truth Table for the circuit with one column for each letter you have used.

Logic Circuit


Start with Inputs A and B.  Complete the table with the different input combinations.

Logic Circuit


Work out the different outputs from your first gate D = A AND B.

Logic Circuit


Now start adding input C.  To make things a little easier, we will assume C is 0 at the moment (we will change it to 1 later).

Logic Circuit


Now work out E = NOT C.

Logic Circuit


Now work out Q = D OR E.

Logic Circuit


Add four more rows to the table and copy the inputs for A, B and D down.

Logic Circuit


Add in the new values for C – 1 this time.

Logic Circuit


Work out the new values for E = NOT C.

Logic Circuit


Finally, work out the missing values for Q = D OR E.

Logic Circuit



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Have a go at completing the Truth Table for this Logic Circuit.

DoIT  Complete the Truth Table


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Have a go at creating this logic diagram using the Logic.ly web site.

Link  Logic.ly


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Last modified: Tuesday, 2 March 2021, 3:56 PM