electronic systems - a1 23/04/2009electronic systems - a1 23/04/2009 2008 ddc - 2006 storey 3 page 3...

Electronic Systems - A1 23/04/2009

2008 DDC - 2006 Storey 1

23/04/2009 - 1 ElnSysA1 - 2008 DDC

ELECTRONIC SYSTEMS

A – INTRODUCTION

A.1 – Organization and contents

» Goals and organization

» Systems and modules

» Analog and digital signals

» Benefits of digital electronics

Politecnico di Torino - ICT school


2008 DDC - 2006 Storey 2Page 2

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INDUSTRIALENGINEERING

DIGITAL ELECTRONICS

MATH, INFORMATICS, PHYSICS, CIRCUITS, .. Basic concepts,

functions, signals, ….

Courses in Electronics

ELECTRONIC SYSTEMS

ELECTRONIC DEVICES

ANALOG ELECTRONICS



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Goals of the “Electronics” courses

• Electronic systems– Basic concepts and techniques.

» Systems as a set of functional units, defined by external parameters (models),

» Use of feedback

» Analog and digital signals and circuits: benefits and drawbacks

» Interfaces and power handling» Examples of applications

• Unique course in electronics for industrial engineers– What can be done with electronics

• First of a sequence for ICT engineers– Applications and design in the following



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Course content

• Electronic systems• Sensors and actuators• Bode plots• Amplification• Control and feedback• Operational amplifiers• Semiconductors and diodes• Field-effect and bipolar transistors• Power electronics



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What you should already know

• Circuit theory– RLC networks with controlled sources, Laplace transform (s)

• Mathematics– Linear equation systems, Differential equations (order I)

• Informatics – Boolean algebra, logic operators

• Physics – Basic mechanics, electric and magnetic fields

• Signal theory– Frequency domain analysis (qualitative)



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Content of this lesson (A1)

• Course goals• Course organization• Exams • Prerequisites• Why “Electronic systems”• An example of system• Function and structure• Signals in the time and frequency domains• Analog and digital signals• Benefits of digital electronic systems



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Course goals

• Develop skills, competencies, and abilities to:

– Translate the application requirements into specifications» how the specific application can be built as an electronic

system

– Design at the system level» functional characteristics, external behavior of modules

» interface among modules

– Design at the circuit level» internal structure of modules

» design flow of modules

» error analysis

– Experimental verification of circuits behavior



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Grouping of course contents

• A Introduction

• B Transducers and amplifiers

• C Operational amplifiers and feedback

• D Electronic devices

• E Logic circuits

• F Processing systems



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Module organization

• Room lessons and exercises– every week:

» 2+2+2+2 h lesson/exercise, or

» 2+2+2 h lesson/exercise +3 h laboratory (to be confirmed)

• Total load (planned)– 15 lessons x 2h 30 + 60 (homework)

– 5 exercises x 2h 10 + 10

– 5 labs x 3h 15 + 8

– total hours 55 78

– 55 room_hours + 78 self-study_hours = 133/27 ≈ 5 credits



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Learning resources – book

• Reference textbook:– Neil Storey

– Electronics: A Systems Approach

– Prentice Hall, 2006, ISBN-13:9780131293960

• student resources– http://wps.pearsoned.co.uk/ema_uk_he_storey_electronic_3/

42/10999/2815814.cw/index.html

– Solved exercises

– Self-evaluation tests



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Learning resources - website

• Course website:– http://ulisse.polito.it/matdid/

3ing_eln_L1740_TO_0/ETLCEnTO/index.htm

– Copies of slides

– Solved exercises, Examples of written tests, …

• FTP site: exchange of reports, homework, ..

• Other suitable textbooks– R.C. Jaeger, T.N. Blalock: Microelectronics

McGraw Hill, 2004

– J. Millman, A. Grabel: Microelectronics (II ed.), McGraw Hill/Boringhieri



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Learning resources in italian

• Course website (same course held in Torino):– http://ulisse.polito.it/matdid/

3ing_eln_L1740_TO_0/ETLCEnTO/index.htm

• Texbook (in italian):– Zappa: Fondamenti di Elettronica (II ed.), Esculapio, 2002

– Zamboni, Graziano: Introduzione all'analisi dei SistemiElettronici, CLUT, 2006 (collection of exercises)

• Distance learning course:– http://corsiadistanza.polito.it/on-line/Sistemi_ele/index2.htm



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Examples and tests

• Examples (during the lesson)– Simple problems, fully solved

• End-of-lesson tests (slide at the end of each lesson)– Test to verify understanding of basis issues, or

– Summary of lesson contents

• Room tests (sessions of exercises)– Statement of a problem

– Sequence of questions

– Require aggregation of contents from several lessons

• Samples of solved written tests (course website)



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Test goals

• Faults must be identified as soon as possible– Before delivery to final customer

– “missed learning” must be corrected before exam

• Goal of tests (self evaluation)– Find quickly “missed learning”

• Goals of exercises – Apply theory to new cases

• An Engineer will carry out design, not exams, but …– To become engineers you have (also) to pass exams

– To pass exams you must be able (also) to solve exercises



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Laboratory experiences: why ?

• Engineering: maths & realworld � models + experiments

• The course includes lab experiments, aimed to– Verify models towards real cases

– Verify correctness of design procedures

– Practice teamworking & communication

• Manuals and guides in the website

• Needs homework– Preliminary workplan, role definition, design, simulations

– Report writing (will be evaluated)



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Exam procedures

• Detailed document “Exams” in the website

• Final mark F– F = 0,8 S + 0,2 L + [miniproject], + [lesson notes prize]

• S: Exam (written exercise + oral discussion)– End of course: single question, about 15’

– Other times: shorter exercise + 30’ oral discussion

• L: lab reports– Unique mark for the whole group

– Penalties for missed experiments



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Cooperation and team-working

• The engineer never works alone: organization and cooperation are part of real work environments

– Lab exercises aim also to exploit cooperation in the workplace: carrying out the experience and writing the report are collective responsibility of the working group.

– Only with proper preliminary organization and task assignment among the people in the group the experiment can be completed in the available time.

– Learn to cooperate effectively and organize your work

– Better to set-up mixed skill & language teams

• the cooperation principle does not apply to exams



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Exam supplement

• A cell-free course

• Each ring � mandatory homework (required to pass the exam)

– Radiation levels of cell phones, comparison with regulations

– Structure and operation of silent bells (vibracall)

– …



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Storey, Electronics: A Systems Approach, 3rd Edition © Pearson Education Limited 20061.20

Electronic systems

� A system can be defined asAny closed volume for which all theinputs and output are known.

� Examples include:– an automotive system– an air conditioner.

� Inputs and outputs will reflect the nature of the system.

1.2



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Systems and modules

• Any electronic system is composed by interconnected modules.

MODULE

MODULE

INTERCONNECTIONS



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?

??

Why do we start from systems ?

• Most designers use modules and functional units designed and/or built by other people.



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Functional units

• To use functional units, one should know the external behavior, not the internal structure.

– What the module does ?» FUNCTION

– How much power is needed ?» POWER SUPPLY

– How is information exchanged with other units ?

» SIGNALS



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What is a “signal” ?

• In electronic systems information is carried byelectric quantities

– Voltages, current

– Frequency, pulse width

– …..

• Information is associated to changes of these quantities:

– Signal

– Any electrical variable with an associated information



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Role of the engineer

• Real-world systems are complex– We need methods to analyze and design them

• The engineer can divide a complex problem in a set of smaller ones � each “small” problem is solvable

• Need to know decomposition and description techniques



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Function and structure

• The system can be described in terms of – Function:� what should the system do� which are interactions (with external world)

– Structure� how the system is built� how can we design and build it

• Described by – Block diagrams

– Object-relations

– Use case



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The sample system

• Example of (low complexity) system:

Air conditioner

– Uses a variety of functional units

– Interface to various sensors and actuators

– A good set of samples for electronic applications

• Steps – Functional definition

– Structure (block diagram)

– Analysis of some functional units



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Functional specification

• What should the system do?– Keep constant temperature in a defined area

• Detailed operations– Measure the air temperature in two positions T1 and T2

– Evaluate a weighted average T = W1 T1 + W2 T2

– Compare with the reference temperature

– Evaluate if heating or cooling is required

– Turn-on heater or cooler

– Activate fan

– Show actual temperature on a LCD display

– ……



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Block diagram / use cases

• Which are the elementary units?– Thermometers

– Heater

– Cooler

– Processing

– User interface (display + knobs/keys)

• How they interact internally and with external world?– Temperature measurements

– Set target, display current temperature

– Turn ON/OFF power devices (cooler, heater)

– Activate fan



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Block diagram and structure

• How is the system built?



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Input sensors

• Temperature measurements– External: air

– Internal: » Refrigerator unit» Motors

• From temperature to voltage (or current)– Temperature sensors, defined by

» Input range,

» Precision» O(I); if linear: gain



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ELECTRONIC SYSTEM

Generic system structure

• Most signal processing used digital circuits– Signals must be converted from analog to digital, than again

to analog:» ANALOG/DIGITAL (A/D) conversion

» DIGITAL/ANALOG (D/A) conversion

DIGITALSYSTEM

A/D D/A

ANALOG SIGNALS



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Signal conversion

• External world: analog• Internal processing: digital



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Output actuators

• Refrigerator motor (ON/OFF)

• Fan (speed control)

• Air flow direction (position control)

• All these are Actuators



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Motor control: functions

• What should a motor control do?



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Motor control: block diagram

• How can we build a motor control system?



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Motor control: electric diagram

• Which are elementary devices, and how are they connected?



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Motor control: device datasheet

• Which are the features of commercial devices used?



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Why do we start from “systems” ?





» SIGNALS



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• Signals (carry information)• Power supply (carry energy)

• The power is distributed as DC voltage (Vsu).

Vsu

GND

INFOIN

INFOOUT

Where does power come from ?



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The power supply system

• Goal: distribute power with– Low heating

– Low pollution (batteries !)

– High efficiency

• Functional units – Mains power supply, batteries, …

– Voltage regulators, battery chargers

– Power handling units

• A complex subsystem



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Why do we start from “systems” ?





» SIGNALS



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Various types of signals

• Analog/digital• High/low/very low level

– Mike vs loudspeaker

• Frequency range– Audio vs RF

• Waveform – Sinewave, squarewave

• Information encoding– Cell phones

– Digital TV

• …



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Signals in the air conditioner

• Input– Temperature

– User setting

• Output– Refrigerator power

– Fan power

– Setting display



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Low frequency signals

• In the circuits handling temperature and position the information changes very slowly: low frequency signals

• Example: sine signal (tone):– v(t) = V sin (ωt + φ)

– V = peak value (volt, V)

– ω = angular frequency (radians/second), (frequency f = ω/2π, hertz, Hz)

– φ = phase (radians, rad)



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Analog signals

• audio

• Triangular wave

• temperature

tempo frequenza



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Radiofrequency signal

• The remote control circuit uses high frequency signals Radio Frequency (RF), around 800 MHz.

– Needs special amplifiers and wiring (coax cables).

• Example: RF carrier at 800 MHz

– Time domain

– Frequency domain

t

1,2 ns

f

800 MHz



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Time domain representation

A signal can be represented in the time domain ….

X axis: time

Y axis:amplitude

instrument: oscilloscope

t = 0



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Frequency domain representation

…. or in the frequency domain:

asse X: frequenza

Y axis:amplitude

Instrument: spectrum analyzer

f = 0

fundamental

II harmonic

III harmonic

noise



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Time-frequency relation

• Quick changes of the signal corresponds to high frequency components

time frequencyF = 0

bandwidth



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Signal spectrum

• Periodic/not periodic» Spectrum with lines (∆F = 1/T) / continuous spectrum

• Limited in the time domain (from t = T1 to t = T2)» Unlimited bandwidth (from f = 0 to f = ∞)

• Limited bandwidth (from fA to fB)» Unlimited in the time domain (from t = -∞ to t = + ∞)

• Steep changes» high frequency components

• Actual signals» ~limited in time & frequency (few power out T1-T2 and F1-F2)

• Spectrum simulator for various waveforms: material � simulator and SW � signal spectrum



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Analog signals

• Analog signals are continuous– in the time domain: is defined for any time instant (within an

assigned interval 0, T)

– in the amplitude domain: can assume any value (within an assigned interval 0, S)

• Parameters:– Amplitude interval

» max and min values (dynamic range),

» DC component (if any)

– Spectral content» bandwidth, spectrum shape t

AS

0

0 T



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Digital signals

• A digital signal is a sequence of numbers, in most cases binary (base 2)

– Discrete in the time domain: defined only at sometime instant (within a defined interval)

– Discrete in the amplitude domain: can assume only some values(within a defined interval)

8 bits, 28 = 256 values

t1

t2

t3

t4

t5




� Discrete signals are often described as digital signals.

� Many digital signals take only two values and are referred to as binary signals.

Representation of digital signals



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Where do we find digital signals ?

• Most evident– Computers and information processing systems

• Most electronic systems contain digital parts– Audio and video equipment

– Cellular and cordless phones

• Embedded electronic systems– Cars

– Planes

– White goods

– …



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Errors with digital representation

• Values defined only at discrete times � Sampling– Sampling interval Ts, sampling rate Fs = 1/Ts

– Can represent signals with bandwidth Fa < Fs/2 (Nyquist-Shannon theorem)

» example: Fs = 20 kHz, Fa < 10 kHz

• Finite number of values � Quantization– N bit : 2N values, therefore

– Quantization error εQ = 100/2N % = 1M/2N PPM» example: 28 = 256 εQ = 0,4 %

• Simulator of quantization effects on Ulisse website at: learning material � simulators and SW � quantization



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Binary signals representation

• Time evolution of a binary signal is represented by a bit sequence:

– Two state symbols 1/0, or H/L

– Defined at Ts intervals (samples)

Ts

valueH

L

time



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Ts

H

L

Timing diagrams

• States are represented by different voltage levels» High state � H, 1, ... → 3 V

» Low state � L, 0, ... → 0,5 V

• The sequence of states becomes a timing diagram, similar to analog signals representation

value

timeH L H H L1 0 1 1 0



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Noise and disturbance

All signals include a variable amount of random noise

the noise does not carry useful information




Distortion

� All systems distort electricalsignal to some extent– examples include clipping,

crossover distortion andharmonic distortion.

� Distortion is systematicand is repeatable.

1.3




� All systems also add noiseto the signals that pass through them.

� Unlike distortion, noise israndom and not repeatable.

� Noise cannot be removed from analog signals

� With proper techniques, noise can be removedfrom digital signals.

Noise



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Analog signal degradation

• Any processing or amplification step adds noise.

• For an analog signal the noise represents a not recoverable information loss.



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Digital signal degradation

• In a digital signal degradation caused by noise can be recovered, if limited within defined boundaries.



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Digital signal level restore

Thanks to amplitude discretization of digital signals, the levels can be restored to original values by comparison with a threshold



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Digital signal recovery

• Digital signal can be recovered at regular intervals– Effects of noise do not cumulate

• Recovery allows to use long digital processing chains, to carry out complex operation

– Not possible with analog technique, due to noise cumulative effects

• To avoid information loss– Noise must be limited

– Signal must be periodically rebuilt.

• Simulator of noise effects on Ulisse website: material � simulator and SW � segnale analogico/digitale con rumore



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Towards external world

• Physical interfaces (transducers and actuators) handle in most cases analog signals

• The Electronic system uses analog signal to interact with the external world

ELECTRONICSYSTEM

ANALOG SIGNALS



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A/D/A sequence

• Today electronics is mainly digital– signals must be translated from analog to digital, and then

from digital to analog:» ANALOG/DIGITAL (A/D) conversion

» DIGITAL/ANALOG (D/A) conversion

ELECTRONIC SYSTEM

NUMERICSYSTEM

A/D D/A

ANALOG SIGNALS



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ELETTRONICSYSTEM

Analog �� Digital �� Analog

• Most part of electronic systems includes:– interfaces towards the analog external world (front-end)

– A/D conversion

– Numeric signal handling

– D/A conversion

– interfaces towards the analog external world (back-end)

ADC

Numeric system DAC

Actuators and analog

back-end

Sensors and analog

front-en



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Changes in electronic systems

• Electronics systems are moving towards digital

A/D

Numericsystem

D/A Actuat

Sens

A/D

Numeric system

Actuators and analog back-end

Sensors and analog

front-end

timeD/A



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Electronics is going towards digital

• Only digital techniques allow complex processing– They do not cumulate noise

– Digital integrated circuit have higher complexity then analog ones

• Automatic tools for design and testing of digital ICs are available

– Digital ICs have lower cost

• The behavior of a digital circuit can be easily modified

– Software

– Programmable logic circuits



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Limits of digital

• Intrinsic errors caused by– Amplitude quantization

(errors related with bit number N),

– Time sampling(errors related with sampling rate).

• Digital variable are represented using analog signals (V, I, …)

– High speed digital signals requires analog techniques

• Some signals can be only analog (RF, …)– The boundary is continuously moving

(over ~1000 MHz almost everything is analog)



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Lesson A1 – final test

• Develop an example of functional (what does) and structural (how is built) descriptions for a system.

• The mains voltage (220V, 50 Hz) can be considered a signal?

• Which part of the spectrum use temperature signals?

• How many values can be represented with 8 bits?

• How are usually represented logic states?

• Describe the benefits of analog signals and systems

• Do all electronic systems have some analog part ?

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