digital logic gates

1. DIGITAL TECHNIQUES
DR. VIKAS DONGRE
HOD ELECTRONICS &TELECOMMUNICATION
GOVERNMENT POLYTECHNIC WASHIM (MS)
EMAIL: DONGREVJ1@GMAIL.COM
M: 9370668979
UNIT2: Logic Gates and Boolean algebra
Subtopic: Logic Gates

2. AND gate
• The AND gate has the above symbol and truth table.
• Two or more input bits produce one output bit.
• All inputs must be true (1) for the output to be true.
• Otherwise the output is false (0).
A B
Input
0 / 1
0
1
OUTPUT

3. 7408- Quad 2 input AND Gate
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
Y=A.B

4. • The OR gate has the following symbol and truth table.
• Two or more input bits produce one output bit.
• Either inputs must be true (1) for the output to be true.
OR gate

5. A B Y
0 0 0
0 1 1
1 0 1
1 1 1
7432- Quad 2 input OR Gate

6. • The NOT gate (or inverter)
• The simplest possible gate is called an "inverter" or a NOT gate.
• One bit as input produces its opposite as output.
• The symbol for a NOT gate is shown below.
• The truth table for the NOT gate shows input and output.

7. 7404- HEX Inverter
A Y
0 1
1 0

8. What happens when you add a NOT
to an AND gate?
A B Y X
0 0 0 1
0 1 0 1
1 0 0 1
1 1 1 0
Y

9. NAND gate

10. A B Y
0 0 1
0 1 1
1 0 1
1 1 0
7400- Quad 2 input NAND Gate

11. What happens when you add a NOT
to an OR gate?
A B X
0 0 1
0 1 0
1 0 0
1 1 0

12. • The NOR gate

13. A B Y
0 0 1
0 1 0
1 0 0
1 1 0
7402- Quad 2 input NOR Gate

14. Exclusive OR gate
• Exclusive OR gate are true if either input is true but not both.
• The Symbol and Truth Table is shown below.
• Output will be high for different inputs
• In general output is high when ODD number of inputs are
high

15. 3 Input X-OR Gate
A B C Y
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 0
1 0 0 1
1 0 1 0
1 1 0 0
1 1 1 1
Y=AΘBΘC

17. A B Y
0 0 0
0 1 1
1 0 1
1 1 0
7486- Quad 2 input XOR Gate

18. Exclusive NOR gate
• The Symbol and Truth Table is shown below.
• Output will be high for same inputs
• In general output is high when EVEN number of
inputs are high

20. A B Y
0 0 1
0 1 0
1 0 0
1 1 1
74266- Quad 2 input X-NOR Gate

21. A B C Y
0 0 0 1
0 0 1 0
0 1 0 0
0 1 1 1
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 0
3 Input X-NOR Gate

22. Assignment:
State IC Number, draw symbol, pin diagram and truth table of
AND, OR, NOT, NAND, NOR,XOR, XNOR GATES

23. Thank you
DR. VIKAS DONGRE
HOD ELECTRONICS &TELECOMMUNICATION
GOVERNMENT POLYTECHNIC WASHIM (MS)
EMAIL: DONGREVJ1@GMAIL.COM
M: 9370668979