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Electronic Devices: Conventional Current Version Floyd 9e ISBN 978-1-29202-564-3 9 781292 025643 Electronic Devices Conventional Current Version Thomas L. Floyd Ninth Edition Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the World Wide Web at: www.pearsoned.co.uk © Pearson Education Limited 2014 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC1N 8TS. All trademarks used herein are the property of their respective owners. The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners. ISBN 10: 1-292-02564-6 ISBN 13: 978-1-292-02564-3 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Printed in the United States of America T RANSISTOR B IAS C IRCUITS Power (kW) Maximum power output 200 180 160 140 120 100 80 60 40 20 0 Furling Shut down 0 Cut in 䊱 5 10 15 20 25 30 35 40 45 Wind speed (mph) Start up F IGURE GA – 5 Example of a wind power curve for a wind turbine. Questions Some questions may require research beyond the content of this coverage. 1. What does HAWT stand for? 2. Why does the input voltage to the ac-to-dc converter vary in amplitude and frequency? 3. What are the physical factors that determine the amount of power available in the wind that strikes the blades of a turbine? 4. What is the Betz limit? 5. In wind farms, how close together should the turbines generally be placed? The following websites are recommended for viewing HAWTs in action. Many other websites are also available. http://www.youtube.com/watch?v=eXejxcW-XGo http://www.youtube.com/watch?v=RFPj9frhKuo http://www.youtube.com/watch?v=7PLvr-lpADM&NR=1 http://www.youtube.com/watch?v=7rlVMJgPRc4 http://www.youtube.com/watch?v=NeVClBaQI_Q http://www.youtube.com/watch?v=PEEAl9laoUg http://www.youtube.com/watch?v=N9_FKGxD27g http://www.youtube.com/watch?v=v05MuBseBQE http://www.youtube.com/watch?v=hBRfboAscww 280 T RANSISTOR B IAS C IRCUITS ANSWERS TO ODD-NUMBERED PROBLEMS (c) Transistor shorted collector-to-emitter 1. Saturation 3. 18 mA 37. (a) 1: 10 V, (d) Open emitter 2: float, 3: -3.59 V, 4: 10 V 7. See Figure ANS–1. (b) 1: 10 V, 2: 4.05 V, 3: 4.75 V, 4: 4.05 V 9. (a) IC(sat) = 50 mA (c) 1: 10 V, 2: 0 V, 3: 0 V, 4: 10 V (b) VCE(CUTOFF) = 10 V (d) 1: 10 V, 2: 570 mV, 3: 1.27 V, 4: float (c) IB = 250 mA; IC = 25 mA; VCE = 5 V (e) 1: 10 V, 2: 0 V, 3: 0.7 V, 4: 0 V (f) 1: 10 V, 2: 0 V, 3: 3.59 V, 4: 10 V 5. VCE = 20 V; IC(sat) = 2 mA 39. R1 open, R2 shorted, BE junction open 41. VC = VCC = 9.1 V, VB normal, VE = 0 V PD(min) = 20 mW 186 k⍀ 45. 457 mW + + 10 V 43. None are exceeded. 1.2 k⍀ – 10 V 47. See Figure ANS–3. – +15 V 䊱 F IGUR E A NS– 1 RC 2.0 k⍀ 11. 63.2 RB 13. IC ⬵ 809 mA; VCE = 13.2 V 2N3904 Nearest standard values assuming βDC = 100 286 k⍀ 15. See Figure ANS–2. VEE +9 V RE 1.0 k⍀ R2 15 k⍀ 䊱 FIGURE ANS–3 49. See Figure ANS–4. 9V R1 47 k⍀ RC 2.2 k⍀ R1 2.0 k⍀ RC 3.0 k⍀ 2N3904 䊱 R2 620 ⍀ F IGUR E A NS– 2 17. (a) -1.63 mA, -8.16 V RE 1.0 k⍀ (b) 13.3 mW 19. VB = -186 mV; VE = -0.886 V; VC = 3.14 V 䊱 21. 0.09 mA FIGURE ANS–4 23. IC = 16.3 mA; VCE = -6.95 V 25. 2.53 kÆ 51. Yes 27. 7.87 mA; 2.56 V 29. ICQ = 92.5 mA; VCEQ = 2.75 V 53. VCEQ will be less, causing the transistor to saturate at a slightly higher temperature, thus limiting the low temperature response. 31. 27.7 mA to 69.2 mA; 6.23 V to 2.08 V; Yes 55. RC open 33. V1 = 0 V, V2 = 0 V, V3 = 8 V 57. R2 open 35. (a) Open collector (b) No problems 59. RC shorted 281 282 BJT A MPLIFIERS APPLICATION ACTIVITY PREVIEW CHAPTER OUTLINE Amplifier Operation Transistor AC Models The Common-Emitter Amplifier The Common-Collector Amplifier The Common-Base Amplifier Multistage Amplifiers The Differential Amplifier Troubleshooting Application Activity GreenTech Application: Wind Power 1 2 3 4 5 6 7 8 CHAPTER OBJECTIVES ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ Describe amplifier operation Discuss transistor models Describe and analyze the operation of common-emitter amplifiers Describe and analyze the operation of common-collector amplifiers Describe and analyze the operation of common-base amplifiers Describe and analyze the operation of multistage amplifiers Discuss the differential amplifier and its operation Troubleshoot amplifier circuits The Application Activity in this chapter involves a preamplifier circuit for a public address system. The complete system includes the preamplifier, a power amplifier, and a dc power supply. You will focus on the preamplifier in this chapter. VISIT THE COMPANION WEBSITE Study aids and Multisim files for this chapter are available at http://www.pearsonhighered.com/electronics INTRODUCTION The things you learned about biasing a transistor are now applied in this chapter where bipolar junction transistor (BJT) circuits are used as small-signal amplifiers. The term small-signal refers to the use of signals that take up a relatively small percentage of an amplifier’s operational range. Additionally, you will learn how to reduce an amplifier to an equivalent dc and ac circuit for easier analysis, and you will learn about multistage amplifiers. The differential amplifier is also covered. KEY TERMS ◆ ◆ ◆ ◆ ◆ ◆ ◆ ◆ r parameter Common-emitter ac ground Input resistance Output resistance Attenuation Bypass capacitor Common-collector ◆ ◆ ◆ ◆ ◆ ◆ Emitter-follower Common-base Decibel Differential amplifier Common mode CMRR (Common-mode rejection ratio) From Chapter 6 of Electronic Devices: Conventional Current Version, Ninth Edition, Thomas L. Floyd. Copyright © 2012 by Pearson Education, Inc. Published by Pearson Prentice Hall. All rights reserved. 283 BJT A MPLIFIERS 1 A MPLIFIER O PE R ATI O N The biasing of a transistor is purely a dc operation. The purpose of biasing is to establish a Q-point about which variations in current and voltage can occur in response to an ac input signal. In applications where small signal voltages must be amplified— such as from an antenna or a microphone—variations about the Q-point are relatively small. Amplifiers designed to handle these small ac signals are often referred to as small-signal amplifiers. After completing this section, you should be able to ❏ ❏ ❏ HISTORY NOTE The American inventor Lee De Forest (1873–1961) is one of several pioneers of radio development. De Forest experimented with receiving longdistance radio signals and in 1907 patented an electronic device named the audion, which was the first amplifier. De Forest’s new three-electrode (triode) vacuum tube boosted radio waves as they were received and made possible what was then called “wireless telephony,” which allowed the human voice, music, or any broadcast signal to be heard. Describe amplifier operation Identify ac quantities ◆ Distinguish ac quantities from dc quantities Discuss the operation of a linear amplifier ◆ Define phase inversion ◆ Graphically illustrate amplifier operation ◆ Analyze ac load line operation AC Quantities In the previous chapters, dc quantities were identified by nonitalic uppercase (capital) subscripts such as IC, IE, VC, and VCE. Lowercase italic subscripts are used to indicate ac quantities of rms, peak, and peak-to-peak currents and voltages: for example, Ic, Ie, Ib, Vc, and Vce (rms values are assumed unless otherwise stated). Instantaneous quantities are represented by both lowercase letters and subscripts such as ic, ie, ib, and vce. Figure 1 illustrates these quantities for a specific voltage waveform. 䊳 FIG UR E 1 Vce can represent rms, average, peak, or peak-to-peak, but rms will be assumed unless stated otherwise. vce can be any instantaneous value on the curve. V rms avg Vce Vce Vce VCE Vce vce 0 t 0 In addition to currents and voltages, resistances often have different values when a circuit is analyzed from an ac viewpoint as opposed to a dc viewpoint. Lowercase subscripts are used to identify ac resistance values. For example, Rc is the ac collector resistance, and RC is the dc collector resistance. You will see the need for this distinction later. Resistance values internal to the transistor use a lowercase r¿ to show it is an ac resistance. An example is the internal ac emitter resistance, r¿e. 284