‫بسم هللا الرحمن الرحيم‬
‫السالم عليكم و رحمة هللا و بركاته‬
IN THE DIGITAL-ORIENTED ERA,
DO WE REALLY NEED ANALOG
CIRCUIT DESIGN?
Muhammad Taher Abuelma’atti
King Fahd University of Petroleum and Minerals
Box 203 Dhahran 31261 Saudi Arabia
mtaher@kfupm.edu.sa
WHAT IS SAID?
• Analog design is old fashion and out of date.
• Analog design is a kind of classic art in a rapidly
changing world of electronics.
• The powerful electronic revolution is toward DSP
rather than ASP.
• It is not wise to select analog design as a career.
• It is not wise to select analog design courses.
• Analog designers are not considered the heroes
of the modern internet and HDTV technology.
• Analog design is used only in high voltage area.
• The world has gone digital and analog is old.
Examples: Digital Camera
• Analog chips translate wavelengths and
intensities into digital code.
• To check the image, the camera
retranslate the digital code into a visual
display.
Examples: Portable Receiver
Design
RF
Filter
Custom Analog IC
Analog
Front-End
A/D
Converter
Custom Digital IC
Digital
Baseband
Processing
A “mostly digital” receiver architecture:
– “Go digital” at the earliest possible stage
Receiver Block Diagram
RF
Filter
Channel
Estimation
RF to
Baseband
High
Speed
A/D
Carrier and
Timing Sync.
Analog IC
Digital IC
Adaptive
Multiuser
Detection
Data Out
3.3 Mbps
Analog RF Design
x
o
0
RF Filter
LNA
o
90
A/D
In Phase
(I)
A/D
Quadrature
(Q)
fosc
AGC
x
Transceivers
Basic Analog Building Blocks:
•
•
•
•
•
•
•
•
•
•
•
1. Amplifiers (Power Amplifiers, Voltage Amplifiers: AF, RF, VF )
2. Oscillators (sinusoidal and others)
3. Filters
4. Clocks
5. Analog-to-Digital and Digital-to-Analog Converters.
6. Modulators (FSK, PSK, ASK, Amplitude, Phase, Frequency
Modulation)
7. Demodulators
8. Mixers
9. Phase Locked Loops
10. Multiplexers.
11. Duplexers
The Reality
• No human experiences reality as a pattern
of 1’s and 0’s.
• The natural world is analog with endlessly
variable waves of sound and light,
temperature and pressure fluctuations,
and shifting magnetic fields.
• Digital revolution drives a strong demand
for advances in analog electronics.
ADVANTAGES OF DIGITAL
CIRCUIT DESIGN
• Robustness; two signal levels.
• Simple and cheap to design; well
developed CAD software.
• Very suitable for integration.
• Offers high precision.
• Programmability can be easily obtained.
• Easy to design at system level.
• Have a cycle/success ratio near unity.
ADVANTAGES OF ANALOG
CIRCUIT DESIGN
• Efficient use of bandwidth.
• Simple; no S/H, A/D and D/A.
• Lower power consumption; uses fewer
transistors.
• Low cost; smaller silicon chips.
• Power efficient.
• Uses physical properties of transistors.
WHEN AND WHERE ANALOG
CIRCUIT DESIGN IS NEEDED?
• To interface a DSP with the input sensors.
• To interface a DSP with the output actuators.
• In low precision systems; analog neural
networks.
• In high frequency systems.
• In enhancing the performance of digital circuits.
On the average, there is probably 15 analog
chips needed for every digital processor.
ANALOG ENHANCED DIGITAL
PERFORMANCE
• Enhancing the performance of the hard
disk drive; by reshaping distorted high
speed digital pulses.
• High speed digital circuits are partly
analog! Relatively large rise and fall times.
• In memory chips and microprocessor
chips entire analog blocks; such as
amplifiers and PLLs are used.
• High frequency clocks.
Digital Enhanced Analog
Performance
• Analog microchip performance can be
improved by integrating them with digital
monitoring and control circuits.
• The line between pure digital and pure
analog chips is rapidly blurring, with both
incorporating a little bit of the other.
• That is Mixed Mode. Experts with feet in
both realm are especially valuable.
MIXED ANALOG AND DIGITAL
CIRCUITS
Advantages
1. Reduced system size.
2. Reduced power dissipation.
3. Increased speed of operation.
4. Increased design flexibility.
5. Increased reliability.
6. Reduced system cost.
CURRENT RESEARCH IN
MAD CIRCUITS
A combination of high dynamic range, high
speed and acceptable low power dissipation
is a challenge for MAD circuits.
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•
•
•
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Analog neural networks.
Field programmable analog arrays.
Radio frequency circuits.
Analog image processing.
Disk drive electronics.
Fuzzy logic.
Chaotic circuits and systems.
WHERE MAD CIRCUITS ARE
USED?
Almost in every broad application where chips are used.
Examples include:
1. Telecommunications: transmission, reception,
switching…
2. Consumer electronics: audio, video,…
3. Computers and related equipment: disk drives, LAN
transmitters and receivers,..
4. Automotive systems: engine control, safety
equipment,…
5. Biomedical instrumentation: hearing aids, cardiac
pacemakers,…
6. Robotics: interfaces to sensors and actuators.
FUTURE OF ANALOG
• The world around us is essentially analog.
• Our senses are organized for communicating with this
world.
• Analog circuit design is indispensable and irreplacable.
• The future of analog circuit design is very dynamic and
holds many opportunities.
• It takes six to nine months for a college graduate to be
productive in digital engineering.
• It takes a Ph.D. holder four years to be productive in the
analog area.
How to Enhance the Image of
Analog Circuit Design
The lack of interest in analog circuit design could be explained by:
1.
2.
3.
4.
5.
Inadequate teaching of the subject. Only teachers with proven
expertise in the area can teach Electronic Circuits courses.
Extensive mathematical manipulations and/or use of the black box
approach. This should be minimized and emphasis should be on
the physical meaning of the equations.
The lack of understanding of circuits at the voltage and current
levels.
Extensive use of simulation and software packages. More
emphasis on experimental work is needed. Simulation is not a
bad thing, but engineering students must feel the real world.
Wrong advises and the advertising media.
CONCLUSION
• Analog circuit design is here to stay.
Imagine the effect on the digital world of a
complete embargo of data converters and
signal-conditioning components by the
small analog nation.
• Analog designers need not leave town.
‫والحمد هلل رب العالمين‬
‫خودا حافظ‬