Electronic systems can be organized into three basic functions: sense, decide, and act. All digital electronics systems operate using only two states - switching electricity on or off. Computers represent information using binary numbers consisting of 1s and 0s. Logic gates like AND, OR, and NOT are used to perform operations on binary inputs and outputs. Combinational logic circuits use logic gates to create functional outputs solely based on the current inputs. Sum of products and Karnaugh maps are conventional methods to design and optimize combinational logic circuits.

2. Electronic Systems Organization
• All electronic systems either manipulate
information, or do work, or do both.
• All electronic systems are organized in a
similar fashion: sense  decide  act
sometimes phrased input  process  output
• Incidentally, all living biological systems
are organized the same way. For
example, your sense organs send
information to the brain which decides and
then sends signals to the muscles, glands
and organs to act.

3. What is digital electronics?
• What does digital mean?
Digit means fingers.
We count with them.
• To understand digital electronics, you
must realize that we can only do 2 things
to electricity between the power source
and the point of use.
Switch it
Regulate it

4. Counting digitally
Decisions are made in digital circuits, by
whether inputs and outputs are switched
on or switched off.
ᵒ On = high = 1 = true
• Off = low = 0 = false
Counting in 1’s and 0’s is called binary.
The reason you need to learn to work with
binary numbers is that computers and all
digital devices keep track of information in
binary.

5. Working with Binary Numbers

6. Hexadecimal Numbers
• People’s brains usually have a difficult
time working with binary numbers.
• Computers don’t work with decimal
numbers like people do.
• Hexadecimal numbers are easy for people
to understand and convert to binary or
decimal easily.
• Hexadecimal is base sixteen, digits from 0
to 15 then a, b, c, d, e, f

7. Hexadecimal Numbers
• Use phonetic values for A through F when
saying a hexadecimal number. This
avoids confusion.
– Alpha, Bravo, Charlie, Delta, Echo, Foxtrot
– Able, Baker, Charlie, Dog, Easy, Fox

8. Hexadecimal conversions

9. Digital versus Analog
• Which is better, digital or analog?
Depends on what you need to do.
• Digital = controlling signals (information)
by switching electricity on or off
• Analog = controlling signals (information)
by regulating electricity

10. Logic Gates
AND
OR
NOT
(inverter)
Truth Tables
Input A Input B Output
false false false
false true false
true true true
true false false
Input A Input B Output
false false false
false true true
true true true
true false true
Input A Output
false true
true false

11. Logic Gates
NAND
NOR
XOR
Truth Tables
Input A Input B Output
false false true
false true true
true false true
true true false
Input A Input B Output
false false true
false true false
true true false
true false false
Input A Input B Output
false false false
false true true
true true false
true false true

12. Counting digitally
Decisions are made in digital circuits, by
whether inputs and outputs are switched
on or switched off.
ᵒ On = high = 1 = true
• Off = low = 0 = false
Counting in 1’s and 0’s is called binary.
The reason you need to learn to work with
binary numbers is that computers and all
digital devices keep track of information in
binary.

14. Combinatorial Logic Circuits

15. Analyzing Combinatorial
Logic Circuits

16. Analyzing Combinatorial
Logic Circuits
Inputs Outputs
A B C 1 2 3 4 5 6
F F F
F F T
F T T
F T F
T T F
T T T
T F T
T F F
Combinatorial
Truth Table

17. Random Combinatorial Circuits
are sub-optimal because
• Circuit function is not obvious
• Using a variety of gates makes parts
planning process difficult and expensive
• Difficult to arrange gates on a PCB or in a
chip
• What is needed is a conventional way to
draw combinatorial logic circuits

18. Sum of the Products

19. Sum of the Products
• Uses AND gates (product) and OR gates
(sum)

20. Sum of the Products
Inputs Outputs
A B C 1 2 3 4
F F F
F F T
F T T
F T F
T T F
T T T
T F T
T F F

22. Logic Families
• All logic gates can be constructed by using
multiple NAND or NOR gates.
• ICs can be divided into two logic families
based on whether they use NAND or NOR
gates.
– TTL and CMOS

23. TTL
• TTL stands for Transistor Transistor Logic
– Based on NPN bipolar transistors
– Current controlled
• Uses NAND gates
– All other gates are built of NAND gates
• TTL chips begin with prefix 74
– SN7400N, SN7438D, SN7402N

24. CMOS
• CMOS refers to MOSFET transistors
– Metal Oxide Silicon Field Effect Transistor
– Voltage Controlled
– Vulnerable to ESD (Electrostatic Discharge)
• Uses NOR gates
– All other gates are built of NOR gates
• Smaller & simpler to build on silicon
• CMOS chips begin with prefix 74C or 40
– TL074CPWR, TS274CDT, CD4081BE

25. Designing Logic Circuits
• Determine a truth table for a safe with an
electronic alarm that will sound an alarm if
the safe is opened after the alarm is set or
if the power is cut and the door is opened,
but not if the alarm is turned off before
opening the door.

27. Optimizing
• More gates in a circuit = more heat &
longer processing time
• Digital or Logic circuits should be
optimized by eliminating any unnecessary
or redundant gates.
• Examining truth tables can help identify
unnecessary gates.