BME – 231
DIGITAL LOGIC DESIGN – EXPERIMENT 2
Introduction to Logic Circuits
Purpose :
1. To study basic logic functions INVERTER, AND, OR, NAND, NOR
2. Study representation of these functions by truth tables, logic diagrams.
Preliminary Work :
1-) Show that 3-input AND gate can be produced with using 2-input AND logic gates. Draw
the circuit and write the truth table of 3-input AND gate.
2-) Prove that 4-input AND gate can be produced with using 2-input AND logic gates. Draw
the circuit and write the truth table of 4-input AND gate.
3-) Show that 3-input OR can be produced with using 2-input OR logic gates. Draw the circuit
and write the truth table of 3-input OR gate.
4-) Prove that 3-input NAND can be produced with using 2-input NAND logic gates. Draw
the circuit and write the truth table of 3-input NAND gate.
Experimental Work :
1-) Using your design in preliminary part 1; construct 3-input AND gate with 2-input AND
logic gates (Hint : you have 7408 AND gate, it has 4 2-input AND gates).Fill the truth table of
3-input AND gate.
x
0
0
0
0
1
1
1
1
y
0
0
1
1
0
0
1
1
z
0
1
0
1
0
1
0
1
F
....
.....
.....
.....
.....
.....
.....
.....
.
2-) Use a 2-input INVERTER and 2-input AND gate; construct a 2-input NAND gate !!! Fill
the truth table of NAND gate
x
y
F
0
0
…..
0
1
…..
1
0
…..
1
1
…..
3-) Use a 2-input NAND gate (7400) fill the truth table of 2-input NAND gate:
x
y
F
0
0
…..
0
1
…..
1
0
…..
1
1
…..
4-) Using your design in preliminary part 2; construct 4-input AND gate with 2-input AND
logic gates (Hint : you have 7408 AND gate, it has 4 2-input AND gates).Fill the truth table of
4-input AND gate.
x
0
0
0
y
0
0
0
z
0
0
1
w
0
1
0
0
0
0
0
0
1
1
1
1
1
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
1
1
1
1
1
0
1
1
1
0
1
F
....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.....
.