Mạch điện tử: Nguyên lý và ứng dụng Electronic Circuits:Fundamentals and application

//SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM Electronic Circuits: Fundamentals and Applications //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM Electronic Circuits:Fundamentals and Applications Second edition Michael Tooley, BA Director of Learning Technology Brooklands College OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM Newnes An imprint of Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier plc group First published 1995 as Electronic Circuits Student Handbook Reprinted 1999 Second edition 2002 ß Michael Tooley 1995, 2002 All rights reserved No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Design and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 0LP Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 7506 5394 Typeset by Integra Software Services Pvt Ltd., Pondicherry 605 005, India www.integra-india.com Printed and bound in Great Britain //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM Contents Preface vii 11 Microprocesser systems 177 A word about safety ix 12 The 555 timer 192 13 Radio 201 Test equipment and measurements 216 Electrical fundamentals Passive components 18 14 D.C circuits 46 Appendix Student assignments 246 Alternating voltage and current 66 Appendix Revision problems 250 Semiconductors 80 Appendix Answers to problems 260 Power supplies 105 Appendix Semiconductor pin connections 263 Amplifiers 116 Appendix Decibels 265 Operational amplifiers 138 Appendix Mathematics for electronics 267 Oscillators 151 Appendix Useful web links 292 Logic circuits 161 Index 10 294 //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM Preface This book has been designed to help you understand how electronic circuits work It will provide you with the basic underpinning knowledge necessary to appreciate the operation of a wide range of electronic circuits including amplifiers, logic circuits, power supplies and oscillators The book is ideal for people who are studying electronics for the first time at any level including a wide range of school and college courses It is equally well suited to those who may be returning to study or who may be studying independently as well as those who may need a quick refresher The book has 14 chapters, each dealing with a particular topic, and seven appendices The approach is topic-based rather than syllabusbased and each major topic looks at a particular application of electronics The relevant theory is introduced on a progressive basis and delivered in manageable chunks In order to give you an appreciation of the solution of simple numerical problems related to the operation of basic circuits, worked examples have been liberally included within the text In addition, a number of problems can be found at the end of each chapter and solutions are provided at the end of the book You can use these end-ofchapter problems to check your understanding and also to give you some experience of the `short answer' questions used in most in-course assessments For good measure, we have included 70 revision problems in Appendix At the end of the book we have included 21 sample coursework assignments These should give you plenty of `food for thought' as well as offering you some scope for further experimentation It is not envisaged that you should complete all of these assignments and a carefully chosen selection will normally suffice If you are following a formal course, your teacher or lecturer will explain how these should be tackled and how they can contribute to your course assessment While the book assumes no previous knowledge of electronics you need to be able to manipulate basic formulae and understand some simple trigonometry in order to follow the numerical examples A study of mathematics to GCSE level (or equivalent) will normally be adequate to satisfy this requirement However, for those who may need a refresher or have had previous problems with mathematics, Appendix will provide you with the underpinning mathematical knowledge required In the later chapters of the book, a number of representative circuits (with component values) have been included together with sufficient information to allow you to adapt and modify the circuits for your own use These circuits can be used to form the basis of your own practical investigations or they can be combined together in more complex circuits Finally, you can learn a great deal from building, testing and modifying simple circuits To this you will need access to a few basic tools and some minimal test equipment Your first purchase should be a simple multi-range meter, either digital or analogue This instrument will allow you to measure the voltages and currents present in your circuits and compare them with predicted values If you are attending a formal course of instruction and have access to an electronics laboratory, make full use of it! A note for teachers and lecturers The book is ideal for students following formal courses (e.g GCSE, AS, A-level, AVCE, BTEC, City and Guilds, RSA, etc.) in schools, sixth-form colleges, and further/higher education colleges It is equally well suited for use as a text that can support distance or flexible learning and for those who may need a `refresher' before studying electronics at a higher level While the book assumes little previous knowledge students need to be able to manipulate basic formulae and understand some simple trigonometry to follow the numerical examples A study of mathematics to GCSE level (or beyond) will normally be adequate to satisfy this requirement However, an appendix has been added specifically to support students who may have difficulty with mathematics Students will require a scientific calculator in order to tackle the end-of-chapter //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM viii PREFACE problems as well as the revision problems that appear at the end of the book We have also included 21 sample coursework assignments These are open-ended and can be modified or extended to suit the requirements of the particular awarding body The assignments have been divided into those that are broadly at Level and those that are at Level In order to give reasonable coverage of the subject, students should normally be expected to complete between four and five of these assignments Teachers can differentiate students' work by mixing assignments from the two levels In order to challenge students, minimal information should be given to students at the start of each assignment The aim should be that of giving students `food for thought' and encouraging them to develop their own solutions and interpretation of the topic Where this text is to be used to support formal teaching it is suggested that the chapters should be followed broadly in the order that they appear with the notable exception of Chapter 14 Topics from this chapter should be introduced at an early stage in order to support formal lab work Assuming a notional delivery time of 4.5 hours per week, the material contained in this book (together with supporting laboratory exercises and assignments) will require approximately two academic terms (i.e 24 weeks) to deliver in which the total of 90 hours of study time should be divided equally into theory (supported by problem solving) and practical (laboratory and assignment work) The recommended four or five assignments will require about 25 to 30 hours of student work to complete Finally, when constructing a teaching programme it is, of course, essential to check that you fully comply with the requirements of the awarding body concerning assessment and that the syllabus coverage is adequate //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± ± [1±10/10] 10.11.2001 4:28PM A word about safety When working on electronic circuits, personal safety (both yours and of those around you) should be paramount in everything that you Hazards can exist within many circuits ± even those that, on the face of it, may appear to be totally safe Inadvertent misconnection of a supply, incorrect earthing, reverse connection of a high-value electrolytic capacitor, and incorrect component substitution can all result in serious hazards to personal safety as a consequence of fire, explosion or the generation of toxic fumes Potential hazards can be easily recognized and it is well worth making yourself familiar with them so that pitfalls can be avoided The most important point to make is that electricity acts very quickly; you should always think carefully before taking any action where mains or high voltages (i.e those over 50 V, or so) are concerned Failure to observe this simple precaution may result in the very real risk of electric shock Voltages in many items of electronic equipment, including all items which derive their power from the a.c mains supply, are at a level which can cause sufficient current flow in the body to disrupt normal operation of the heart The threshold will be even lower for anyone with a defective heart Bodily contact with mains or high-voltage circuits can thus be lethal The most severe path for electric current within the body (i.e the one that is most likely to stop the heart) is that which exists from one hand to the other The hand-to-foot path is also dangerous but somewhat less dangerous than the hand-to-hand path Before you start to work on an item of electronic equipment, it is essential not only to switch off but to disconnect the equipment at the mains by removing the mains plug If you have to make measurements or carry out adjustments on a piece of working (or `live') equipment, a useful precaution is that of using one hand only to perform the adjustment or to make the measurement Your `spare' hand should be placed safely away from contact with anything metal (including the chassis of the equipment which may, or may not, be earthed) The severity of electric shock depends upon several factors including the magnitude of the current, whether it is alternating or direct current, and its precise path through the body The magnitude of the current depends upon the voltage which is applied and the resistance of the body The electrical energy developed in the body will depend upon the time for which the current flows The duration of contact is also crucial in determining the eventual physiological effects of the shock As a rough guide, and assuming that the voltage applied is from the 250 V 50 Hz a.c mains supply, the following effects are typical: Current Physiological effect less than mA mA to mA Not usually noticeable Threshold of perception (a slight tingle may be felt) Mild shock (effects of current flow are felt) Serious shock (shock is felt as pain) Motor nerve paralysis may occur (unable to let go) Respiratory control inhibited (breathing may stop) Ventricular fibrillation of heart muscle (heart failure) mA to mA mA to 10 mA 10 mA to 20 mA 20 mA to 50 mA more than 50 mA It is important to note that the figures are quoted as a guide ± there have been cases of lethal shocks resulting from contact with much lower voltages and at relatively small values of current It is also worth noting that electric shock is often accompanied by burns to the skin at the point of contact These burns may be extensive and deep even when there may be little visible external damage to the skin The upshot of all this is simply that any potential in excess of 50 V should be considered dangerous Lesser potentials may, under unusual circumstances, also be dangerous As such, it is wise to get into the habit of treating all electrical and electronic circuits with great care //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-CH000-PRELIMS.3D ± 10 ± [1±10/10] 10.11.2001 4:28PM //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 252 ± [246±293/48] 10.11.2001 4:57PM 252 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS Figure A2.7 Figure A2.8 Figure A2.5 Figure A2.9 Figure A2.6 Figure A2.10 //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 253 ± [246±293/48] 10.11.2001 4:57PM APPENDIX REVISION PROBLEMS 28 29 Figure A2.11 30 Figure A2.12 31 32 33 34 35 36 Figure A2.13 27 An inductor of 100 mH is connected in series with a variable capacitor If the capacitor is variable over the range 50 pF to 500 pF, 37 253 determine the maximum and minimum values of resonant frequency for the circuit [Page 74] An audio amplifier delivers an output power of 40 W r.m.s to an  resistive load What r.m.s voltage will appear across the load? [Page 8] A transformer has 400 primary turns and 60 secondary turns The primary is connected to a 220 V a.c supply and the secondary is connected to a load resistance of 20  Assuming that the transformer is perfect, determine: (a) the secondary voltage; (b) the secondary current; and (c) the primary current [Page 75] Figure A2.13 shows the characteristic of a diode Determine the resistance of the diode when (a) VF ˆ V and (b) IF ˆ mA [Page 84] A transistor operates with a collector current of 25 mA and a base current of 200 mA Determine: (a) the value of emitter current; (b) the value of common-emitter current gain; and (c) the new value of collector current if the base current increases by 50% [Page 93] A zener diode rated at 5.6 V is connected to a 12 V d.c supply via a fixed series resistor of 56  Determine the current flowing in the resistor, the power dissipated in the resistor and the power dissipated in the zener diode [Page 112] An amplifier has identical input and output resistances and provides a voltage gain of 26 dB Determine the output voltage produced if an input of 50 mV is applied [Page 265] Figure A2.14 shows the frequency response of an amplifier Determine the mid-band voltage gain and the upper and lower cut-off frequencies [Page 119] Figure A2.15 shows the frequency response of an amplifier Determine the bandwidth of the amplifier [Page 120] The transfer characteristic of a transistor is shown in Fig A2.16 Determine (a) the static value of common-emitter current gain at IC ˆ 50 mA and (b) the dynamic (smallsignal) value of common-emitter current gain at IC ˆ 50 mA [Page 127] The output characteristics of a bipolar transistor are shown in Fig A2.17 If the transistor operates with VCC ˆ 15 V, RL ˆ 500  and IB ˆ 40 mA determine: //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 254 ± [246±293/48] 10.11.2001 4:57PM 254 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS Figure A2.14 Figure A2.15 (a) the quiescent value of collector±emitter voltage; (b) the quiescent value of collector current; (c) the peak±peak output voltage produced by a base input current of 40 mA [Page 131] 38 The output characteristics of a field effect transistor are shown in Fig A2.18 If the transistor operates with VDD ˆ 18 V, RL ˆ k and VGS ˆ À1:5 V determine: (a) the quiescent value of drain±source voltage; //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 255 ± [246±293/48] 10.11.2001 4:57PM APPENDIX REVISION PROBLEMS 255 Figure A2.16 Figure A2.17 (b) the quiescent value of drain current; (c) the peak±peak output voltage produced by a gate input voltage of V pk±pk; (d) the voltage gain of the stage [Page 130] 39 Figure A2.19 shows the circuit of a commonemitter amplifier stage Determine the values of IB , IC , IE and the voltage at the emitter [Page 130] //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 256 ± [246±293/48] 10.11.2001 4:57PM 256 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS Figure A2.18 40 41 A transistor having hie ˆ 2:5 k and hfe ˆ 220 is used in a common-emitter amplifier stage with RL ˆ 3:3 k Assuming that hoe and hre are negligible, determine the voltage gain of the stage [Page 128] An astable multivibrator is based on coupling capacitors C1 ˆ C2 ˆ 10 nF and timing resistors R1 ˆ 10 k and R2 ˆ k 42 43 44 45 46 47 48 49 Figure A2.19 Determine the frequency of the output signal [Page 155] A sine wave oscillator is based on a Wien bridge with R ˆ k and C ˆ 15 nF Determine the frequency of the output signal [Page 153] The frequency response characteristic of an operational amplifier is shown in Fig A2.20 If the device is configured for a closed-loop gain of 200, determine the resulting bandwidth [Page 142] Redraw Fig A2.21 using American (MIL/ ANSI) symbols [Page 164] Draw the truth table for the logic gate arrangement shown in Fig A2.22 [Page 165] Redraw Fig A2.23 using BS symbols [Page 164] What single logic gate can be used to replace the logic circuit shown in Fig A2.24? [Page 165] What single logic gate can be used to replace the logic circuit shown in Fig A2.25? [Page 165] Devise arrangements of logic gates that will produce the truth tables shown in Fig A2.26 Use the minimum number of logic gates in each case [Page 165] //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 257 ± [246±293/48] 10.11.2001 4:57PM APPENDIX REVISION PROBLEMS Figure A2.20 Figure A2.23 Figure A2.21 Figure A2.24 Figure A2.22 Figure A2.25 257 //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 258 ± [246±293/48] 10.11.2001 4:57PM 258 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS Figure A2.26 Figure A2.27 50 51 52 53 54 A kHz square wave clock waveform is applied to the circuit shown in Fig A2.27 Sketch the output waveform against a labelled time axis [Page 166] (a) Convert 7B hexadecimal to binary (b) Convert 11000011 binary to hexadecimal [Page 179] What is the largest value, expressed (a) in decimal, and (b) in binary, that can appear at any one time on a 16-bit data bus [Page 179] Sketch a diagram showing the basic arrangement of a microprocessor system Label your drawing clearly [Page 178] (a) Explain the function of a microprocessor clock (b) Explain why a quartz crystal is used to determine the frequency of a microprocessor clock [Page 184] 55 56 57 58 59 60 Sketch the circuit diagram of a typical microprocessor clock Label your drawing clearly [Page 183] Explain, briefly, how a microprocessor fetches and executes instructions Illustrate your answer with a timing diagram showing at least one fetch±execute cycle [Page 184] Sketch the circuit diagram of a monostable timer based on a 555 device Explain, briefly, how the circuit operates [Page 194] A 555 timer is connected in monostable mode If the values of the timing components used are C ˆ 100 nF and R ˆ 10 k, determine the monostable pulse time [Page 194] Determine the frequency of a radio signal that has a wavelength of 1500 m [Page 202] Determine the wavelength of a radio signal that has a frequency of 40 MHz [Page 202] //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 259 ± [246±293/48] 10.11.2001 4:57PM APPENDIX REVISION PROBLEMS 61 62 63 64 65 66 67 68 69 Figure A2.28 70 259 A superhet medium wave broadcast receiver with an intermediate frequency of 470 kHz is to cover the frequency range 560 kHz to 1.58 MHz Over what frequency range should the local oscillator be tuned? [Page 207] Explain, with the aid of waveforms, the operation of a simple AM demodulator [Page 209] Explain, with the aid of a labelled sketch, how the voltage and current are distributed in a half-wave dipole aerial [Page 210] Determine the length of a half-wave dipole for use at a frequency of 70 MHz [Page 210] Sketch the block schematic of a simple TRF radio receiver Briefly explain the function of each stage [Page 206] A moving coil meter has a full-scale deflection current of mA and a coil resistance of 400  Determine the value of the multiplier resistor if the meter is to be used as a voltmeter reading to 15 V [Page 216] A moving coil meter has a full-scale deflection current of mA and a coil resistance of 120  Determine the value of shunt resistor if the meter is to be used as an ammeter reading to 20 mA [Page 217] Explain the term `ohms-per-volt' as applied to a voltmeter [Page 219] Sketch the circuit of a simple ohmmeter based on a moving coil meter [Page 217] Identify each of the forms of distortion shown in Fig A2.28 [Page 240] //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 260 ± [246±293/48] 10.11.2001 4:57PM Appendix Answers to problems Chapter 1.1 coloumbs, joules, hertz 1.2 3.6 MJ 1.3 0.52 radian 1.4 11:46 1.5 39:57 k 1.6 0.68 H 1.7 2.45 nF 1.8 0.19 mA 1.9 4:75  10À4 V 1.10 16:5  106  1.11 4:8  106 , 7:2  103 ,  103 , 0:5  10À3 1.12 silver 1.13 33.3 mA 1.14 6.72 V 1.15 3:3 k 1.16 15  1.17 0:436  1.18 0.029 W 1.19 0.675 W 1.20 57.7 mA 1.21 0:625  106 V/m 1.22 12 A 1.23 mWb Chapter 2.1 60 , 3.75 W, wirewound 2.2 270 k 5%, 10  10%, 6:8 M 5%, 0:39  5%, 2:2 k 2% 2.3 44:65  to 49:35  2.4 27  and 33  in series, 27  and 33  in parallel, 56  and 68  in series, 27  33  and 56  in parallel, 27  33  and 68  in series 2.5 66:67  2.6 10  2.7 102 , 78:5  2.8 407:2  2.9 98:7 k 2.10 3:21  10À4 2.11 3:3 mF and 4:7 mF in parallel, mF and 10 mF in parallel, mF 3:3 mF 4:7 mF and 10 mF in parallel, 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 mF and 10 mF in series, 3:3 mF and 4:7 mF in series 60 pF, 360 pF 50 pF 20.79 mC 1.98 nF 69:4 mF 0.313 V 0.136 H 0.48 J 10 mH 22 mH and 60 mH in parallel, 10 mH and 22 mH in parallel, 10 mH and 22 mH in series, 10 mH and 60 mH in series, 10 mH 60 mH and 100 mH in series Chapter 3.1 275 mA 3.2 200  3.3 1.5 A away from the junction, 215 mA away from the junction 3.4 1.856 V, 6.6 V 3.5 0.1884 A, 0.1608 A, 0.0276 A, 5.09 V, 0.91 V, 2.41 V 3.6 1.8 V, 10.2 V 3.7 0.5 A, 1.5 A 3.8 V, V, V, V, V 3.9 1:5 k, 60 mA 3.10 40.6 ms 3.11 3.54 s 3.12 112:1 mF 3.13 0.128 s 3.14 2.625 V,  3.15 21 V, , A,  3.16 50 mA, 10 V 3.17 50 V, 10 V Chapter 4.1 ms, 35.35 V 4.2 59.88 Hz, 3394 V 4.3 50 Hz 30 V pk±pk, 15 Hz 10 V pk±pk, 150 kHz 0.1 V pk±pk 4.4 19 V, À11:8 V 4.5 10.6 V //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 261 ± [246±293/48] 10.11.2001 4:57PM APPENDIX ANSWERS TO PROBLEMS 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 36:19 k, 144:76  3.54 mA 10:362 , 1:45 k 4.71 V 592:5 , 0.186 A 0.55, 0.487 A 157 nF 1.77 MHz to 7.58 MHz 7.5 mA, 2.71 V 281 kHz, 41.5, 6.77 kHz 18 V 245 V Chapter 5.1 silicon (forward threshold appx 0.6 V) 5.2 41 , 150  5.4 9.1 V zener diode 5.5 250  5.6 germanium low-power high-frequency, silicon low-power low-frequency, silicon high-power low-frequency, silicon low-power high frequency 5.7 2.625 A, 20 5.8 mA, 19.6 5.9 16.7 5.10 BC108 5.11 mA, 1.1 mA 5.12 47 mA, 94, 75 5.13 12.5 mA, 12 V, 60 mA 5.14 16 mA Chapter 6.1 80 mV 6.2 mV 6.3 200  6.4 12.74 V, 9.1 V, 8.4 V 6.5 36.4 mA, 0.33 W 6.6 V, 12.04 V, V 6.7 0:5 , 8.3 V 6.8 1%, 15.15 V Chapter 7.1 40, 160, 6400, 100  7.2 2V 7.3 56, 560 kHz, 15 Hz 7.4 18.5 7.5 0.0144 7.6 2.25 V 7.7 13 mA, 3.39 V, 2.7 V, 4.51 V 7.8 V, mA, 8.5 V 7.9 12.2 V, 6.1 mA, 5.5 V Chapter 8.1 10 V 8.2 40 dB, 600 kHz 8.3 200 k 8.4 ‡1 V, À1 V, V, À2 V, ‡2 V, V 8.5 kHz, 100 Hz 8.6 11, 8.7 10, 3.38 kHz, 338 kHz Chapter 9.1 4.44, 40 9.2 6:49 k 9.3 18 k 9.4 5.63 V pk±pk 9.5 14:3 k, 42:9 k Chapter 10 10.9 Low-power Schottky (LS) TTL, 27th Month of 1989 10.10 0.6 V Chapter 11 11.1 00111010 11.2 C2 11.3 (c) 11.4 048 576 11.5 1024 11.6 ‡127 11.7 (a) Input port, FEH (a) Output port, FFH (b) 001010000 Chapter 12 12.5 (a) VR2 (b) S2 (c) R4 (d) VR1 (e) S1 (f) R2 (g) VR3 (h) R5 (i) C10 (j) C5 and R3 12.6 50  Chapter 13 13.1 1.58 m 13.2 23.1 MHz 13.3 4m 13.4 1.02 MHz to 2.07 MHz 13.5 10.7 MHz, 170 kHz, 63 13.6 (a) L1/C2 (b) R1/R2 261 //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 262 ± [246±293/48] 10.11.2001 4:57PM 262 13.7 13.8 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS (c) L2 (d) R4/C5 (e) VR1 (f) C6 (g) C7 (h) C1 3m 24 W Chapter 14 14.1 19:6 k 14.2 11:11  14.3 16:67 k 14.4 100 k 14.5 (a) 19.99 V (b) 10 mV 14.6 25 k 14.7 60 mA 14.8 35:3 mA 14.9 (a) 3.33 ms, V (b) 125 ns, 150 mV 14.10 (a) 7:8 ms (b) 3:4 ms (c) 4:4 ms (d) 1:5 ms (e) ms (f) V //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 263 ± [246±293/48] 10.11.2001 4:57PM Appendix Semiconductor pin connections Figure A4.1 Diodes Figure A4.2 Transistors //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 264 ± [246±293/48] 10.11.2001 4:57PM 264 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS Figure A4.3 Figure A4.4 Integrated circuits //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 265 ± [246±293/48] 10.11.2001 4:57PM Appendix Decibels Decibels (dB) are a convenient means of expressing gain (amplification) and loss (attenuation) in electronic circuits In this respect, they are used as a relative measure (i.e comparing one voltage with another, one current with another, or one power with another) In conjunction with other units, decibels are sometimes also used as an absolute measure Hence dBV are decibels relative to V, dBm are decibels relative to mW, etc The decibel is one-tenth of a bel which, in turn, is defined as the logarithm, to the base 10, of the ratio of output power (Pout ) to input power (Pin ) Gain and loss may be expressed in terms of power, voltage and current such that: AP ˆ Pout Vout Iout AV ˆ and AI ˆ Pin Vin Iin where AP , AV or AI is the power, voltage or current gain (or loss) expressed as a ratio, Pin and Pout are the input and output powers, Vin and Vout are the input and output voltages, and Iin and Iout are the input and output currents Note, however, that the powers, voltages or currents should be expressed in the same units/multiples (e.g Pin and Pout should both be expressed in W, mW, mW or nW) It is often more convenient to express gain in decibels (rather than as a simple ratio) using the following relationships: AP ˆ 10 log10 (Pout ) (Vout ) AV ˆ 20 log10 (Pin ) (Vin ) and AI ˆ 20 log10 (Iout ) (Iin ) Note that a positive result will be obtained whenever Pout , Vout , or Iout is greater than Pin , Vin , or Iin , respectively A negative result will be obtained whenever Pout , Vout , or Iout is less than Pin , Vin or Iin A negative result denotes attenuation rather than amplification A negative gain is thus equivalent to an attenuation (or loss) If desired, the formulae may be adapted to produce a positive result for attenuation simply by inverting the ratios, as shown below: AP ˆ 10 log10 (Pin ) (Vin ) AV ˆ 20 log10 (Pout ) (Vout ) and AI ˆ 20 log10 (Iin ) (Iout ) where AP , AV or AI is the power, voltage or current gain (or loss) expressed in decibels, Pin and Pout are the input and output powers, Vin and Vout are the input and output voltages, and Iin and Iout are the input and output currents Note, again, that the powers, voltages or currents should be expressed in the same units/multiples (e.g Pin and Pout should both be expressed in W, mW, mW or nW) It is worth noting that, for identical decibel values, the values of voltage and current gain can be found by taking the square root of the corresponding value of power gain As an example, a voltage gain of 20 dB results from a voltage ratio of 10 while a power gain of 20 dB corresponds to a power ratio of 100 Finally, it is essential to note that the formulae for voltage and current gain are only meaningful when the input and output impedances (or resistances) are identical Voltage and current gains expressed in decibels are thus only valid for matched (constant impedance) systems The following table gives some useful decibel values: Decibels (dB) Power gain (ratio) Voltage gain (ratio) Current gain (ratio) 10 13 16 1.26 1.58 2.51 3.16 3.98 5.01 6.31 7.94 10 19.95 39.81 1.12 1.26 1.41 1.58 1.78 2.24 2.51 2.82 3.16 3.98 6.31 1.12 1.26 1.41 1.58 1.78 2.24 2.51 2.82 3.16 3.98 6.31 //SYS21/G:/ECF/REVISES (5-11-2001)/0750653949-APPENDIX.3D ± 266 ± [246±293/48] 10.11.2001 4:57PM 266 ELECTRONIC CIRCUITS: FUNDAMENTALS AND APPLICATIONS Decibels (dB) Power gain (ratio) Voltage gain (ratio) Current gain (ratio) 20 30 40 50 60 70 100 1000 10 000 100 000 000 000 10 000 000 10 31.62 100 316.23 1000 3162.3 10 31.62 100 316.23 1000 3162.3 Example A5.1 An amplifier with matched input and output resistances provides an output voltage of V for an input of 25 mV Express the voltage gain of the amplifier in decibels Solution The voltage gain can be determined from the formula: AV ˆ 20 log10 (Vin /Vout ) where Vin ˆ 20 mV and Vout ˆ mV Thus: AV ˆ 20 log10 (20 mV/1 mV) ˆ 20 log10 (20) ˆ 20  1:3 ˆ 26 dB Example A5.3 An amplifier provides a power gain of 33 dB What output power will be produced if an input of mW is applied? Solution Here we must re-arrange the formula to make Pout the subject, as follows: AP ˆ 10 log10 (Pout /Pin ) AV ˆ 20 log10 (Vout /Vin ) thus where Vin ˆ 25 mV and Vout ˆ V Thus: AP /10 ˆ log10 (Pout /Pin ) AV ˆ 20 log10 (1 V/25 mV) ˆ 20 log10 (40) ˆ 20  1:6 ˆ 32 dB or Example A5.2 A matched 600  attenuator produces an output of mV when an input of 20 mV is applied Determine the attenuation in decibels Solution The attenuation can be determined by applying the formula: antilog10 (AP /10) ˆ Pout /Pin Hence Pout ˆ Pin  antilog10 (AP /10) Now Pin ˆ mW ˆ 20  10À3 W and AP ˆ 33 dB, thus Pout ˆ  10À3  antilog10 (33/10) ˆ  10À3  antilog10 (3:3) ˆ  10À3  1:995  10À3 ˆ 3:99 W ... [1±10/10] 10.11.2001 4:28PM Electronic Circuits:Fundamentals and Applications Second edition Michael Tooley, BA Director of Learning Technology Brooklands College OXFORD AUCKLAND BOSTON JOHANNESBURG... which exists from one hand to the other The hand-to-foot path is also dangerous but somewhat less dangerous than the hand-to-hand path Before you start to work on an item of electronic equipment,... measure the voltages and currents present in your circuits and compare them with predicted values If you are attending a formal course of instruction and have access to an electronics laboratory,