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Diodes

Diodes. 1 . Basic diode concept. 2 . Load-line analysis of diode circuit. 3 . Zener-diode voltage regulator circuit. 4 . Ideal-diode model. 5 . Applications of diodes. BASIC DIODE CONCEPTS. A pn junction. Drift and diffusion currents in a pn junction. Figure 9.7.

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Diodes

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  1. Diodes 1. Basic diode concept. 2. Load-line analysis of diode circuit. 3. Zener-diode voltage regulator circuit. 4. Ideal-diode model. 5. Applications of diodes.

  2. BASIC DIODE CONCEPTS

  3. A pn junction

  4. Drift and diffusion currents in a pn junction

  5. Figure 9.7 Forward- and reverse-biased pn junctions

  6. Figure 9.8, 9.9 Semiconductor diode i-v characteristic Semiconductor diode circuit symbol

  7. Figure 9.10 The i-v characteristic of the semiconductor diode

  8. Shockley Equation k = 1.38 × 10–23 J/K is Boltzmann’s constant and q = 1.60 × 10–19 C is the magnitude of the electrical charge of an electron. At a temperature of 300 K, we have

  9. Exercise 10.1At a temperature of 300K, a certain junction diode has iD = 0.1mA for vD = 0.6V. Assume that n is unity and use VT = 0.026V. find the value of the saturation current Is.

  10. LOAD-LINE ANASYSIS OF DIODE CIRCUITS

  11. LOAD-LINE ANALYSIS OF DIODE CIRCUITS By applying KVL, we get But two unknowns, we need one more equation relating iD and vD to solve the problem.

  12. Example 10.1If the circuit of Figure 10.5 has Vss = 2V, R = 1kW, and a diode with the characteristic shown in Figure 10.7, find the diode voltage and current at the operating point.Example 10.2Repeat Example 10.1 if Vss = 10V, R = 10kW

  13. Vss = i R + VD Vss = 2, R = 1k Vss=10, R=10k

  14. ZENER-DIODE VOLTAGE-REGULATOR CIRCUITS

  15. What is a Zener diode?

  16. Zener Diodes Diodes that are intended to operate in the breakdown region are called Zener diodes.

  17. Breakdown region

  18. ZENER-DIODE VOLTAGE-REGULATOR CIRCUITS A voltage regulator circuit provides a nearly constant voltage to a load from a variable source.

  19. Example 10.3The voltage-regulator circuit of Figure 10.9 has R = 1kW and use a Zener diode having the characteristic shown in Figure 10.10. Find the output voltage for Vss = 15V. Repeat for Vss = 20V.

  20. R = 1k Vss + i R +VD = 0 i = 0, VD = -Vss VD = 0, i = Vss/R

  21. IDEAL-DIODE MODEL

  22. IDEAL-DIODE MODEL The ideal diode acts as a short circuit for forward currents and as an open circuit with reverse voltage applied.

  23. Figure 9.11 Large-signal on/off diode model

  24. Figure 9.12, 9.13, 9.14 Circuit containing ideal diode Circuit of Figure 9.12, assuming that the ideal diode conducts Figure 9.13 Circuit of Figure 9.12, assuming that the ideal diode does not conduct Figure 9.14

  25. Figure 9.15, 9.16, 9.17 Figure 9.16 Figure 9.17

  26. Summary of Guidelines to analysis ideal-diode circuits

  27. APPLICATION OF DIODES

  28. Figure 9.45 DC power supply

  29. RECTIFIER CIRCUITS

  30. Half-Wave Rectifier Circuits

  31. Figure 9.20, 9.21 Ideal diode rectifier input and output voltages

  32. As Vs reaches VB, then diode starts to conduct

  33. Full-Wave Rectifier Circuits

  34. Full-wave rectifier

  35. Figure 9.42 Operation of bridge rectifier

  36. Figure 9.49 • A Zener diode voltage regulator; • (b) simplified circuit for Zener regulator

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