Digital Logic & Design

Dr. Waseem Ikram

Lecture 06

Recap

Logic Gates Basic Building Blocks Symbol Performs unique function Represented by a function/truth table Function expression Timing Diagram

Recap

AND Gate F=A.B OR Gate F=A+B NOT Gate AND Gate enables/disables device OR Gate car door alarm system NOT Gate 1’s complement

AF

Recap

Alternate Symbolic representations NAND Gate NOT-AND operation Universal NAND Gate NOR Gate NOT-OR operation Universal NOR Gate

BAF

BAF

NOR Universal Gate

Input Output

A B F

0 0 0

0 1 1

1 0 1

1 1 1

1 2

NOR Universal Gate

31

2

Input Output

A B F

0 0 0

0 1 0

1 0 0

1 1 1

NAND-NOR Universal Gate

31

24 3

1

2

4

NAND Gate Applications

Device Failure Alarm

ALARM

NOR Gate Applications

Washing Machine Controller

Switch

XOR Gate

1 output 2 inputs Multiple inputs

=10

0

0

XOR Gate function

Input Output

A B F

0 0 0

0 1 1

1 0 1

1 1 0

BAF

XOR Gate Timing Diagram

t0 t4 t5 t6t1 t2 t3

XNOR Gate

1 output 2 inputs Multiple inputs

=0

0

0

XNOR Gate function

Input Output

A B F

0 0 1

0 1 0

1 0 0

1 1 1

BAF

XNOR Gate Timing Diagram

t0 t4 t5 t6t1 t2 t3

XOR Gate Applications

Detecting odd number of 1’s

1

2

3

A

B

C

D

XNOR Gate Applications

Detecting even number of 1’s

1

2

3

A

B

C

D

TTL/CMOS NOT Gate

+VCC

+VVo/p

Vi/p

+VDD

Vi/pVo/p

NPNTransistor N-Type

MOSFET

P-TypeMOSFET

Type of IC Logic Gates

74XX00 Quad 2-input NAND Gate 74XX02 Quad 2-input NOR Gate 74XX04 Hex Inverter 74XX08 Quad 2-input AND Gate 74XX10 Triple 3-input NAND Gate 74XX11 Triple 3-input AND Gate 74XX20 Dual 4-input NAND Gate

Type of IC Logic Gates

74XX21 Dual 2-input AND Gate 74XX27 Triple 3-input NOR Gate 74XX30 Single 8-input NAND Gate 74XX32 Quad 2-input OR Gate 74XX86 Quad 2-input XOR Gate 74XX133 Single 13-input NAND Gate

Logic Gate Integrated Circuits

1 2 3 4 5 6 7

891011121314

7400Four 2-Input NAND Gate

1 2 3 4 5 6 7

891011121314

7404Hex Inverters

1 2 3 4 5 6 7

7408Four 2-Input AND Gate

891011121314

1 2 3 4 5 6 7

891011121314

7432Four 2-Input OR Gate

Logic Gate Integrated Circuits

1 2 3 4 5 6 7

891011121314

7486Four 2-Input XOR Gate

1 2 3 4 5 6 7

891011121314

74266Four 2-Input XNOR Gate

1 2 3 4 5 6 7

7402Four 2-Input NOR Gate

891011121314

Integrated Circuits (IC)

CMOS Complementary Metal Oxide Logic TTL Transistor-Transistor Logic ECL Emitter Coupled Logic PMOS p-channel MOS transistor NMOS n-channel MOS transistor E2CMOS

Operational Characteristics

DC Supply Voltage Noise Margin Power Dissipation Frequency Response Fan Out