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

6. A pn junction

7. Drift and diffusion currents in a pn junction

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

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

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

13. 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

14. 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.

15. LOAD-LINE ANASYSIS OF DIODE CIRCUITS

17. 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.

19. 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

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

21. ZENER-DIODE VOLTAGE-REGULATOR CIRCUITS

22. What is a Zener diode?

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

24. Breakdown region

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

26. 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.

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

28. IDEAL-DIODE MODEL

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

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

32. 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

33. Figure 9.15, 9.16, 9.17 Figure 9.16 Figure 9.17

34. Summary of Guidelines to analysis ideal-diode circuits

35. APPLICATION OF DIODES

36. Figure 9.45 DC power supply

37. RECTIFIER CIRCUITS

38. Half-Wave Rectifier Circuits

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

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

45. Full-Wave Rectifier Circuits

48. Full-wave rectifier

49. Figure 9.42 Operation of bridge rectifier

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