The document discusses digital logic gates. It describes the basic logic gates - AND, OR, NOT - and their functions and truth tables. It also discusses alternate representations like NAND and NOR gates. Applications of logic gates in devices like counters and alarms are provided.

1. DIGITAL LOGIC DESIGN
LECTURE 04
BY-FARHAT ULLAH

2. LOGIC GATES
A logic gate is an electronic device
implementing a Boolean function,
a logical operation performed on one or more
binary inputs that produces a single binary
output.
When a transistor is on, or open, then an
electric current can flow through. And when it's
off, then no current flows.
When you string a bunch of these transistors
together, then you get what's called a logic
gate, which lets you add, subtract, multiply,
and divide binary numbers in any way
imaginable

3. AND GATE
1 output
2 inputs
3 inputs
4 inputs
Multiple inputs
&0
0
0

4. AND GATE FUNCTION
Logical Multiplication function
Input Output
A B F
0 0 0
0 1 0
1 0 0
1 1 1
BAF 
NCBAF  ....

5. AND GATE TIMING DIAGRAM
t0 t4 t5 t6t1 t2 t3
A
B
F

6. OR GATE
1 output
2 inputs
3 inputs
4 inputs
Multiple inputs
>=10
0
0

7. OR GATE FUNCTION
Boolean Add function
Input Output
A B F
0 0 0
0 1 1
1 0 1
1 1 1
BAF 
NCBAF  ..

8. OR GATE TIMING DIAGRAM
t0 t4 t5 t6t1 t2 t3
A
B
F

9. NOT GATE
1 input
1 output

10. NOT GATE FUNCTION
Invert function
Input Output
A F
0 1
1 0
AF 

11. NOT GATE TIMING DIAGRAM
t0 t4 t5 t6t1 t2 t3
A
F

12. AND GATE APPLICATIONS
Enable/Disable Device
 Counter counts when it receives pulses
U/D
Reset
B1
B8
Carry out
ENB
Counter
A
B
Clock Pulses
Enable
Disable

13. OR GATE APPLICATIONS
Car door open alarm
Alarm
Front left door
Rear left door
Front right door
Rear right door

14. NOT GATE APPLICATIONS
1’s Complement
1 1 1 1
1 1 1 1
0 0
0 0
0
0 0
0

15. ALTERNATE REPRESENTATIONS

16. NAND GATE
1 output
2 inputs
3 inputs
4 inputs
Multiple inputs
&0
0
0

17. NAND GATE FUNCTION
NOT-AND function
Input Output
A B F
0 0 1
0 1 1
1 0 1
1 1 0
BAF 
NCBAF  ....

18. NAND GATE TIMING DIAGRAM
t0
t4
t5
t6
t1
t2
t3
A
B
F

19. NAND UNIVERSAL GATE
Input Output
A B F
0 0 1
0 1 1
1 0 1
1 1 0

20. NAND UNIVERSAL GATE
1 2
Input Output Output
A B F1 F
0 0 1 0
0 1 1 0
1 0 1 0
1 1 0 1

21. NAND UNIVERSAL GATE
3
1
2
Input Output
A B F
0 0 0
0 1 1
1 0 1
1 1 1

22. NOR GATE
1 output
2 inputs
3 inputs
4 inputs
Multiple inputs
>=10
0
0

23. NOR GATE FUNCTION
NOT-OR function
Input Output
A B F
0 0 1
0 1 0
1 0 0
1 1 0
BAF 
NCBAF  ....

24. NOR GATE TIMING DIAGRAM
t0 t4 t5 t6t1 t2 t3