الرحمن الله بسمالرحيم

رحمة و عليكم السالمبركاته الله و

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• Analog design is old fashion and out of date.• Analog design is a kind of classic art in a rapidly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

A “mostly digital” receiver architecture:– “Go digital” at the earliest possible stage

AnalogFront-End

A/DConverter

DigitalBaseband

Processing

RFFilter

Custom Analog IC Custom Digital IC

Receiver Block Diagram

RF to Baseband

High Speed

A/D

RFFilter

Analog IC

Carrier and Timing Sync.

ChannelEstimation

AdaptiveMultiuserDetection

Data Out3.3 Mbps

Digital IC

Analog RF Design

x

x

090

o

o

LNA AGC

fosc

In Phase (I)

Quadrature(Q)

RF Filter

A/D

A/D

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 CIRCUITSAdvantages

1. Reduced system size.

2. Reduced power dissipation.

3. Increased speed of operation.

4. Increased design flexibility.

5. Increased reliability.

6. Reduced system cost.

A combination of high dynamic range, highspeed and acceptable low power dissipationis a challenge for MAD circuits.

• Analog neural networks.• Field programmable analog arrays.• Radio frequency circuits.• Analog image processing.• Disk drive electronics.• Fuzzy logic.• Chaotic circuits and systems.

CURRENT RESEARCH IN MAD CIRCUITS

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. Inadequate teaching of the subject. Only teachers with proven expertise in the area can teach Electronic Circuits courses.

2. 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.

3. The lack of understanding of circuits at the voltage and current levels.

4. 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.

5. 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.

رب لله والحمدالعالمين

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