Digital and Analog Quantities
Graph of an analog quantity
(temperature versus time).
Graph of an analog quantity
(temperature versus time).
Types of electronic devices or
instruments:
• Analog
• Digital
• Combination analog and digital
Audio Signal Amplification
Analog Reproduction of Music
Audio Signal
Simplified basic block diagram for a tabletcounting and bottling control system
Advantages of digital circuits
• Fast process time.
• Fast transmission time.
• Large storage capability.
Advantages of digital circuits
• The conventional numbering
system uses ten digits: 0,1, 2, 3,
4, 5, 6, 7, 8, and 9.
• The binary numbering system
uses just two digits: 0 and 1.
Binary Digits & Logic Levels
• The two binary digits are
designated 0 and 1
• They can also be called LOW and
HIGH,
where LOW = 0 and HIGH = 1
Digital Pulse
• Binary values are also represented
by voltage levels by voltage levels
Major Parts (Important Items) of
a Digital Pulse
•
•
•
•
•
Base line
Amplitude
Rise time (tr)
Pulse width (tw)
Fall time (tf)
Nonideal Pulse
• A nonideal pulse typical of those found in
actual digital circuits
5.0 V
4.5 V
Amplitude
= 5.0 V 2.5 V
0.0 V
4.5 V
tw
Pulse width
2.5 V
0.5 V
0.5 V
tr
Rise
time
tf
Fall
time
Information on Important Items
• Rise time, tr - time required to go from LOW to
HIGH.
• Fall time, tf - time required to go from HIGH to
LOW.
• Amplitude – height measured between HIGH
and LOW (or vice versa). Measurement for rise
and fall time usually made within 10% to 90% of
pulse amplitude.
• Pulse width, tw - duration of pulse, measured at
50% points on the rising and falling edges.
Logic level ranges of voltage for
a digital circuit.
TTL input and output voltage
specifications
• Input or output voltages that fall within the shaded region
of Figure below are undefined voltages and cannot be
distinguished as a logic LOW or logic HIGH by the IC’s
circuitry.
5.0 V
5.0 V
LOGIC 1
LOGIC 1
2.4 V
2.0 V
0.8 V
0V
Invalid
output voltage
Invalid
input voltage
LOGIC 0
0.4 V
0V
LOGIC 0
(a)
(b)
TTL input (a) and output (b) voltage specifications
Digital Waveforms
• tw = pulse width
• T = period of the waveform
• f = frequency of the waveform
Digital Waveforms characteristics
•
A) Periodic Square Wave (repeating the same waveform at a fixed interval, called
period (T))
B) Nonperiodic Square Wave (opposite to periodic, where the waveform does not repeat
itself at a fixed interval)
Digital Waveforms Carry Binary
Information
Clock and Timing Diagram
• Clock –a basic timing waveform that is used to
synchronize all waveforms in digital systems
• Must be periodic!!!
• Used to synchronize all waveforms in digital systems
• Each interval between pulses in clock equals the time for
one bit
• It, itself does not carry any information
• Timing diagram –a graph of digital waveforms showing
the actual time relationship of two or more waveforms,
and how each waveform changes in relation to the
others
Timing Diagram: A Graph of
Digital Waveforms
Serial Transfer of Binary Data.
• Data are transferred in serial form from one point to
another
• Serial transfer of 8 bits data from computer to modem. t0 to
t1 is first.
• Slow. Why??–The data have to transferred one by one
• Advantage:–Requires only one line
Parallel Transfer of Binary Data
• Data are transferred in parallel form from one
point to another
• During transfer, all the bits in a group are sent
out on separate lines simultaneously
• Fast. Why??
– A few bits can be sent at one time
• Disadvantage:
– Requires a few lines
Parallel Transfer of Binary Data
(Cont.)
• Parallel transfer of 8 bits of binary data from
computer to printer. The beginning time is t0.
Fixed Function Integrated Circuits I
• Monolithic – all components on a single chip –
diode, transistor, resistor, capacitor.
• Fixed-function logic – logic function have been
fixed by the manufacturer. Need to refer spec
sheet before using it / cannot be changed.
• Opposite of fixed function = Programmable
Logic Devices (PLDs)
• Programmable logic – logic function can be
changed based on the program that we write
into the IC.
Fixed Function Integrated Circuits I
(Cont.)
Cutaway view of one type of fixed-function IC package
showing the chip mounted inside, with connection to input
an output pins.
Fixed Function Integrated Circuits II
• Examples of through-hole and surface-mounted devices. The DIP is
larger than the SOIC with the same number of leads. This particular DIP
is approximately 0.785in. long, and the SOIC is approximately 0.385 in.
long.
Fixed Function Integrated Circuits II
(Cont.)
• Flat pack with straight leads
Fixed Function Integrated Circuits III
• Pin 1 always marked by an identifier like
small dot, a notch, or beveled edge
IC Packages
• DIP (Dual In Line) –the most common.
• SMT (Surface Mount Technology) – eg.
Small outline integrated circuit (SOIC),
PLCC (Plastic leaded chip carrier), LCCC
(Leadless ceramic chip carrier).
• Others: SSOP, TSSOP and TVSOP
Complexity Classification for
Fixed-Function ICs
• SSI (Small-scale integration) – 10 gates
• MSI (Medium-scale integration) – 10 - 100
gates
• LSI (Large-scale integration) – 100 10,000 gates
• VLSI (Very large-scale integration) –
10,000 - 100,000 gates
• ULSI (Ultra large-scale integration) –
>100,000 gates
Digital Logic Families
• The two most widely used logic families are TTL,
transistor-transistor logic, and CMOS,
complementary metal-oxide semiconductor.
• TTL had been the leading IC family in the smallscale and medium-scale integration categories
until its leading position was challenged by the
CMOS family.
• The CMOS family belongs to the category of
unipolar digital ICs because it uses p- and nchannel MOSFETs as the main circuit element.