Electronic Devices & Circuits - CH03.pdf - 3 S PECIAL-P URPOSE D IODES CHAPTER OUTLINE 31 32 33 34 35 36 VISIT THE COMPANION WEBSITE The Zener Diode

Electronic Devices & Circuits - CH03.pdf - 3 S PECIAL-P...

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3 S PECIAL -P URPOSE D IODES CHAPTER OUTLINE 3–1 The Zener Diode 3–2 Zener Diode Applications 3–3 The Varactor Diode 3–4 Optical Diodes 3–5 Other Types of Diodes 3–6 Troubleshooting Application Activity Green Tech Application 3: Solar Power CHAPTER OBJECTIVES Describe the characteristics of a zener diode and analyze its operation Apply a zener diode in voltage regulation Describe the varactor diode characteristic and analyze its operation Discuss the characteristics, operation, and applications of LEDs, quantum dots, and photodiodes Discuss the basic characteristics of several types of diodes Troubleshoot zener diode regulators KEY TERMS VISIT THE COMPANION WEBSITE Study aids and Multisim files for this chapter are available at INTRODUCTION Chapter 2 was devoted to general-purpose and rectifier diodes, which are the most widely used types. In this chapter, we will cover several other types of diodes that are designed for specific applications, including the zener, varactor (variable- capacitance), light-emitting, photo, laser, Schottky, tunnel, pin, step-recovery, and current regulator diodes. APPLICATION ACTIVITY PREVIEW The Application Activity in this chapter is the expansion of the 16 V power supply developed in Chapter 2 into a 12 V regulated power supply with an LED power-on indicator. The new circuit will incorporate a voltage regulator IC, which is introduced in this chapter. Zener diode Zener breakdown Varactor Light-emitting diode (LED) Electroluminescence Pixel Photodiode Laser
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T HE Z ENER D IODE 113 3–1 T HE Z ENER D IODE A major application for zener diodes is as a type of voltage regulator for providing stable reference voltages for use in power supplies, voltmeters, and other instruments. In this section, you will see how the zener diode maintains a nearly constant dc voltage under the proper operating conditions. You will learn the conditions and limitations for properly using the zener diode and the factors that affect its performance. After completing this section, you should be able to Describe the characteristics of a zener diode and analyze its operation Recognize a zener diode by its schematic symbol Discuss zener breakdown Define avalanche breakdown Explain zener breakdown characteristics Describe zener regulation Discuss zener equivalent circuits Define temperature coefficient Analyze zener voltage as a function of temperature Discuss zener power dissipation and derating Apply power derating to a zener diode Interpret zener diode datasheets The symbol for a zener diode is shown in Figure 3–1. Instead of a straight line repre- senting the cathode, the zener diode has a bent line that reminds you of the letter Z (for zener). A zener diode is a silicon pn junction device that is designed for operation in the reverse-breakdown region. The breakdown voltage of a zener diode is set by carefully con- trolling the doping level during manufacture. Recall, from the discussion of the diode char-
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