1. Advanced Digital design
Lecture1
Assist. Prof. Rassim Suliyev - SDU 2018

2. Course Materials
All needed Software and course materials will be located on inside the Advanced Digital Design directory
Materials that are used in this slides are taken from the textbook “Digital Electronics A Practical Approach with VHDL” by William Kleitz

3. INTRODUCTION Digital circuitry is the foundation of digital computers
Home appliances, alarm systems
heating systems, automated machine control
inventory management, medical electronics, etc…
Digital electronics evolved from transistor circuitry
easily be fabricated
designed to output one of two voltage levels
1 - HIGH (usually +5 volts)
0 – LOW (usually 0 Volts)

4. Digital versus Analog Systems
operate on discrete digits
numbers
letters
symbols
etc…
deal strictly with ON and OFF
represent by 0s and 1s
Analog
measure and respond to continuously varying electrical or physical magnitudes
Temperature
Pressure
Velocity
Position
Etc…

5. Digital versus Analog Systems
So why do we need to use digital representations in a world that is naturally analog?

6. Digital Representations of Analog Quantities

7. Noises

8. Review Questions
Complete the following sentences with the word analog or digital:
Wind speed is an example of a(an) _______ quantity?
A music CD contains _______ information?
A USB connector transmits _______ data?
Hourly outdoor air temperatures exhibit _______ variations?
An automobile speedometer display is (digital, analog, or could be either)
An analog-to-digital converter outputs an analog voltage. True or false?

9. Number Conversions
binary
octal
hexadecimal

10. BCD and Symbol Represenation
The binary-coded-decimal (BCD) system is used to represent each of the 10 decimal digits as a 4-bit binary code. This code is useful for outputting to displays that are always numeric (0 to 9), such as those found in digital clocks or digital voltmeters.
ASCII - American Standard Code for Information Interchange The ASCII code uses 7 bits to represent all the alphanumeric data used in computer I/O.

11. Digital Signals
A digital signal is made up of a series of 1s and 0s that represent numbers, letters, symbols, or control signals

12. Clock Waveform Timing
Special clock and timing circuits are used to produce clock waveforms to trigger the digital signals at precise intervals

13. Serial vs Parallel uses a single electrical conductor
can only transmit 1 bit for each clock period
generally used in computer- to-computer communication
uses a separate electrical conductor for each bit to be transmitted, thus is fast
generally used in data transfer inside the computer

14. Review Questions
Why is ASCII code required by digital computer systems?
What is the relationship between clock frequency and clock period?
What advantage does parallel have over serial in the transmission of digital signals?

15. Switches in Electronic Circuits
transitions between 0 and 1 are caused by switching from one voltage level to another (0V, 5V)
make and break a connection between two electrical conductors
manual switch
electromechanical relay
semiconductor devices (diodes, transistors)

16. A Relay as a Switch controlled by external voltage
often used to deliver signals to a high power load

17. A Relay as a Switch
Advantage: it provides total isolation between the triggering source and the output
Disadvantages:
High power consumption (triggering device must supply several mA whereas a semiconductor requires only a few uA to operate)
Speed (take several ms to switch, compared to us for a semiconductor switch)

18. A Diode as a Switch
semiconductor device that allows current to flow only in one direction
current will flow only if the anode is more positive than the cathode

19. 1. Determine if the diodes are forward or reverse biased?
2. Determine V1-V6 (with respect to ground) for the circuits?

20. A Transistor as a Switch
three-terminal semiconductor component
allows an input signal at one of its terminals to cause the other two terminals to become a short or an open circuit
commonly made of silicon
N-type (one more electron)
P-type (one less electron)
three distinct regions
emitter, base, collector
N-P-N-type or P-N-P

21. NPN vs PNP NPN transistor
applying a positive voltage from base to emitter causes the collector-to-emitter junction to short (turn ON)
applying a negative voltage or 0 V from base to emitter causes the collector-to-emitter junction to open (turn OFF)
PNP transistor
applying a negative voltage from base to emitter turns it ON.
applying a positive voltage or 0 V from base to emitter turns it OFF

22. A Transistor as a Switch

23. The TTL Integrated Circuit
TTL (Transistor–transistor logic)
use a combination of several transistors, diodes, and resistors integrated together in a single package
Q1 - input transistor (drives Q2)
Q2 controls Q3 and Q4
D1 protects Q1
from negative voltages
D2 ensures Q4 cut off
when Q3 is saturated

24. The idea of needing a variable RC resistance is accommodated by the TTL integrated circuit. It uses another transistor (Q4) in place of RC to act like a varying resistance. Q4 is cut off (acts like a high RC) when the output transistor (Q3) is saturated, and then Q4 is saturated (acts like a low RC) when Q3 is cut off.

25. The CMOS Integrated Circuit
CMOS – complementary metal oxide semiconductor
uses a complementary pair of metal oxide semiconductor field-effect transistors (MOSFETs)
advantage is its low power consumption
disadvantages compared to TTL:
switching speed is slower
burnout due to electrostatic charges
Details about TTL and CMOS
discussed later in further lectures

26. Integrated Circuit Chips

27. Review Questions
How does a normally open relay differ from a normally closed relay?
To forward bias a diode, the anode is made more ___________ (positive/negative) than the cathode.
To turn ON an NPN transistor, a ___________ (positive/negative) voltage is applied to the base.

28. Simulation of Switching Circuits
MultiSIM - software simulation tool
provides an accurate simulation of digital and analog circuit operation
simulation of instruments to measure IC, component, and circuit characteristics
Download and install from:
Follow Advanced Digital Design -> Software directories

30. Grading Policy MT1 – 30% MT2 – 30% FIN – 40%
Class work (until week 8) – 15%
Paper based Midterm (on week 8) – 15%
MT2 – 30%
Class work (weeks ) – 15%
Attendance (weeks 1-15) – 15%
FIN – 40%
Project – 20%
Paper based Final Exam – 20%