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Diodes 1.

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Presentation on theme: "Diodes 1."— Presentation transcript:

1 Diodes 1

2 sedr42021_0301a.jpg Figure 3.1 The ideal diode: (a) diode circuit symbol; (b) i–v characteristic; (c) equivalent circuit in the reverse direction; (d) equivalent circuit in the forward direction. Microelectronic Circuits - Fifth Edition Sedra/Smith

3 sedr42021_0302a.jpg Figure 3.2 The two modes of operation of ideal diodes and the use of an external circuit to limit the forward current (a) and the reverse voltage (b). Microelectronic Circuits - Fifth Edition Sedra/Smith

4 sedr42021_0303a.jpg Figure 3.3 (a) Rectifier circuit. (b) Input waveform. (c) Equivalent circuit when vI  0. (d) Equivalent circuit when vI  0. (e) Output waveform. Microelectronic Circuits - Fifth Edition Sedra/Smith

5 sedr42021_e0301.jpg Figure E3.1 Microelectronic Circuits - Fifth Edition Sedra/Smith

6 sedr42021_e0302.jpg Figure E3.2 Microelectronic Circuits - Fifth Edition Sedra/Smith

7 sedr42021_0304a.jpg Figure 3.4 Circuit and waveforms for Example 3.1.
Microelectronic Circuits - Fifth Edition Sedra/Smith

8 sedr42021_0305a.jpg Figure 3.5 Diode logic gates: (a) OR gate; (b) AND gate (in a positive-logic system). Microelectronic Circuits - Fifth Edition Sedra/Smith

9 sedr42021_0306a.jpg Figure 3.6 Circuits for Example 3.2.
Microelectronic Circuits - Fifth Edition Sedra/Smith

10 sedr42021_e0304a.jpg Figure E3.4 Microelectronic Circuits - Fifth Edition Sedra/Smith

11 sedr42021_e0305.jpg Figure E3.5 Microelectronic Circuits - Fifth Edition Sedra/Smith

12 sedr42021_0307.jpg Figure 3.7 The i–v characteristic of a silicon junction diode. Microelectronic Circuits - Fifth Edition Sedra/Smith

13 sedr42021_0308.jpg Figure 3.8 The diode i–v relationship with some scales expanded and others compressed in order to reveal details. Microelectronic Circuits - Fifth Edition Sedra/Smith

14 sedr42021_0309.jpg Figure 3.9 Illustrating the temperature dependence of the diode forward characteristic. At a constant current, the voltage drop decreases by approximately 2 mV for every 1C increase in temperature. Microelectronic Circuits - Fifth Edition Sedra/Smith

15 sedr42021_e0309.jpg Figure E3.9 Microelectronic Circuits - Fifth Edition Sedra/Smith

16 sedr42021_0310.jpg Figure A simple circuit used to illustrate the analysis of circuits in which the diode is forward conducting. Microelectronic Circuits - Fifth Edition Sedra/Smith

17 sedr42021_0311.jpg Figure Graphical analysis of the circuit in Fig using the exponential diode model. Microelectronic Circuits - Fifth Edition Sedra/Smith

18 sedr42021_0312.jpg Figure Approximating the diode forward characteristic with two straight lines: the piecewise-linear model. Microelectronic Circuits - Fifth Edition Sedra/Smith

19 sedr42021_0313a.jpg Figure Piecewise-linear model of the diode forward characteristic and its equivalent circuit representation. Microelectronic Circuits - Fifth Edition Sedra/Smith

20 sedr42021_0314.jpg Figure The circuit of Fig with the diode replaced with its piecewise-linear model of Fig Microelectronic Circuits - Fifth Edition Sedra/Smith

21 sedr42021_0315.jpg Figure Development of the constant-voltage-drop model of the diode forward characteristics. A vertical straight line (B) is used to approximate the fast-rising exponential. Observe that this simple model predicts VD to within 0.1 V over the current range of 0.1 mA to 10 mA. Microelectronic Circuits - Fifth Edition Sedra/Smith

22 sedr42021_0316a.jpg Figure The constant-voltage-drop model of the diode forward characteristics and its equivalent-circuit representation. Microelectronic Circuits - Fifth Edition Sedra/Smith

23 sedr42021_e0312.jpg Figure E3.12 Microelectronic Circuits - Fifth Edition Sedra/Smith

24 sedr42021_0317a.jpg Figure Development of the diode small-signal model. Note that the numerical values shown are for a diode with n = 2. Microelectronic Circuits - Fifth Edition Sedra/Smith

25 sedr42021_0318a.jpg Figure (a) Circuit for Example 3.6. (b) Circuit for calculating the dc operating point. (c) Small-signal equivalent circuit. Microelectronic Circuits - Fifth Edition Sedra/Smith

26 sedr42021_0319.jpg Figure 3.19 Circuit for Example 3.7.
Microelectronic Circuits - Fifth Edition Sedra/Smith

27 sedr42021_e0316.jpg Figure E3.16 Microelectronic Circuits - Fifth Edition Sedra/Smith

28 sedr42021_tb0301.jpg Table 3.1 Modeling the Diode Forward Characteristic Microelectronic Circuits - Fifth Edition Sedra/Smith

29 sedr42021_tb0307.jpg Table 3.1 (Continued)
Microelectronic Circuits - Fifth Edition Sedra/Smith

30 sedr42021_0320.jpg Figure 3.20 Circuit symbol for a zener diode.
Microelectronic Circuits - Fifth Edition Sedra/Smith

31 sedr42021_0321.jpg Figure The diode i–v characteristic with the breakdown region shown in some detail. Microelectronic Circuits - Fifth Edition Sedra/Smith

32 sedr42021_0322.jpg Figure 3.22 Model for the zener diode.
Microelectronic Circuits - Fifth Edition Sedra/Smith

33 sedr42021_0323a.jpg Figure (a) Circuit for Example 3.8. (b) The circuit with the zener diode replaced with its equivalent circuit model. Microelectronic Circuits - Fifth Edition Sedra/Smith

34 sedr42021_0324.jpg Figure 3.24 Block diagram of a dc power supply.
Microelectronic Circuits - Fifth Edition Sedra/Smith

35 sedr42021_0325a.jpg Figure (a) Half-wave rectifier. (b) Equivalent circuit of the half-wave rectifier with the diode replaced with its battery-plus-resistance model. (c) Transfer characteristic of the rectifier circuit. (d) Input and output waveforms, assuming that rD ! R. Microelectronic Circuits - Fifth Edition Sedra/Smith

36 sedr42021_0326a.jpg Figure Full-wave rectifier utilizing a transformer with a center-tapped secondary winding: (a) circuit; (b) transfer characteristic assuming a constant-voltage-drop model for the diodes; (c) input and output waveforms. Microelectronic Circuits - Fifth Edition Sedra/Smith

37 sedr42021_0327a.jpg Figure The bridge rectifier: (a) circuit; (b) input and output waveforms. Microelectronic Circuits - Fifth Edition Sedra/Smith

38 sedr42021_0328a.jpg Figure (a) A simple circuit used to illustrate the effect of a filter capacitor. (b) Input and output waveforms assuming an ideal diode. Note that the circuit provides a dc voltage equal to the peak of the input sine wave. The circuit is therefore known as a peak rectifier or a peak detector. Microelectronic Circuits - Fifth Edition Sedra/Smith

39 sedr42021_0329a.jpg Figure Voltage and current waveforms in the peak rectifier circuit with T. The diode is assumed ideal. Microelectronic Circuits - Fifth Edition Sedra/Smith

40 sedr42021_0330.jpg Figure Waveforms in the full-wave peak rectifier. Microelectronic Circuits - Fifth Edition Sedra/Smith

41 sedr42021_0331a.jpg Figure The “superdiode” precision half-wave rectifier and its almost-ideal transfer characteristic. Note that when vI > 0 and the diode conducts, the op amp supplies the load current, and the source is conveniently buffered, an added advantage. Not shown are the op-amp power supplies. Microelectronic Circuits - Fifth Edition Sedra/Smith

42 sedr42021_0332.jpg Figure General transfer characteristic for a limiter circuit. Microelectronic Circuits - Fifth Edition Sedra/Smith

43 sedr42021_0333.jpg Figure Applying a sine wave to a limiter can result in clipping off its two peaks. Microelectronic Circuits - Fifth Edition Sedra/Smith

44 sedr42021_0334.jpg Figure 3.34 Soft limiting.
Microelectronic Circuits - Fifth Edition Sedra/Smith

45 sedr42021_0335.jpg Figure 3.35 A variety of basic limiting circuits.
Microelectronic Circuits - Fifth Edition Sedra/Smith

46 sedr42021_e0327.jpg Figure E3.27 Microelectronic Circuits - Fifth Edition Sedra/Smith

47 sedr42021_0336.jpg Figure The clamped capacitor or dc restorer with a square-wave input and no load. Microelectronic Circuits - Fifth Edition Sedra/Smith

48 sedr42021_0337.jpg Figure The clamped capacitor with a load resistance R. Microelectronic Circuits - Fifth Edition Sedra/Smith

49 sedr42021_0338a.jpg Figure Voltage doubler: (a) circuit; (b) waveform of the voltage across D1. Microelectronic Circuits - Fifth Edition Sedra/Smith

50 sedr42021_0339.jpg Figure Simplified physical structure of the junction diode. (Actual geometries are given in Appendix A.) Microelectronic Circuits - Fifth Edition Sedra/Smith

51 sedr42021_0340.jpg Figure Two-dimensional representation of the silicon crystal. The circles represent the inner core of silicon atoms, with +4 indicating its positive charge of +4q, which is neutralized by the charge of the four valence electrons. Observe how the covalent bonds are formed by sharing of the valence electrons. At 0 K, all bonds are intact and no free electrons are available for current conduction. Microelectronic Circuits - Fifth Edition Sedra/Smith

52 sedr42021_0341.jpg Figure At room temperature, some of the covalent bonds are broken by thermal ionization. Each broken bond gives rise to a free electron and a hole, both of which become available for current conduction. Microelectronic Circuits - Fifth Edition Sedra/Smith

53 sedr42021_0342a.jpg Figure A bar of intrinsic silicon (a) in which the hole concentration profile shown in (b) has been created along the x-axis by some unspecified mechanism. Microelectronic Circuits - Fifth Edition Sedra/Smith

54 sedr42021_0343.jpg Figure A silicon crystal doped by a pentavalent element. Each dopant atom donates a free electron and is thus called a donor. The doped semiconductor becomes n type. Microelectronic Circuits - Fifth Edition Sedra/Smith

55 sedr42021_0344.jpg Figure A silicon crystal doped with a trivalent impurity. Each dopant atom gives rise to a hole, and the semiconductor becomes p type. Microelectronic Circuits - Fifth Edition Sedra/Smith

56 sedr42021_0345a.jpg Figure (a) The pn junction with no applied voltage (open-circuited terminals). (b) The potential distribution along an axis perpendicular to the junction. Microelectronic Circuits - Fifth Edition Sedra/Smith

57 sedr42021_0346.jpg Figure The pn junction excited by a constant-current source I in the reverse direction. To avoid breakdown, I is kept smaller than IS. Note that the depletion layer widens and the barrier voltage increases by VR volts, which appears between the terminals as a reverse voltage. Microelectronic Circuits - Fifth Edition Sedra/Smith

58 sedr42021_0347.jpg Figure The charge stored on either side of the depletion layer as a function of the reverse voltage VR. Microelectronic Circuits - Fifth Edition Sedra/Smith

59 sedr42021_0348.jpg Figure The pn junction excited by a reverse-current source I, where I > IS. The junction breaks down, and a voltage VZ , with the polarity indicated, develops across the junction. Microelectronic Circuits - Fifth Edition Sedra/Smith

60 sedr42021_0349.jpg Figure The pn junction excited by a constant-current source supplying a current I in the forward direction. The depletion layer narrows and the barrier voltage decreases by V volts, which appears as an external voltage in the forward direction. Microelectronic Circuits - Fifth Edition Sedra/Smith

61 sedr42021_0350.jpg Figure Minority-carrier distribution in a forward-biased pn junction. It is assumed that the p region is more heavily doped than the n region; NA @ ND. Microelectronic Circuits - Fifth Edition Sedra/Smith

62 sedr42021_0351.jpg Figure 3.51 The SPICE diode model.
Microelectronic Circuits - Fifth Edition Sedra/Smith

63 sedr42021_0352.jpg Figure Equivalent-circuit model used to simulate the zener diode in SPICE. Diode D1 is ideal and can be approximated in SPICE by using a very small value for n (say n = 0.01). Microelectronic Circuits - Fifth Edition Sedra/Smith

64 sedr42021_0353.jpg Figure Capture schematic of the 5-V dc power supply in Example 3.10. Microelectronic Circuits - Fifth Edition Sedra/Smith

65 sedr42021_0354.jpg Figure The voltage vC across the smoothing capacitor C and the voltage vO across the load resistor Rload = 200  in the 5-V power supply of Example 3.10. Microelectronic Circuits - Fifth Edition Sedra/Smith

66 sedr42021_0355.jpg Figure The output-voltage waveform from the 5-V power supply (in Example 3.10) for various load resistances: Rload = 500 , 250 , 200 , and 150 . The voltage regulation is lost at a load resistance of 150 . Microelectronic Circuits - Fifth Edition Sedra/Smith

67 sedr42021_e0335a.jpg Figure E3.35 (a) Capture schematic of the voltage-doubler circuit (in Exercise 3.35). Microelectronic Circuits - Fifth Edition Sedra/Smith

68 sedr42021_e0335b.jpg Figure E3.35 (Continued) (b) Various voltage waveforms in the voltage-doubler circuit. The top graph displays the input sine-wave voltage signal, the middle graph displays the voltage across diode D1, and the bottom graph displays the voltage that appears at the output. Microelectronic Circuits - Fifth Edition Sedra/Smith

69 sedr42021_p03002a.jpg Figure P3.2 Microelectronic Circuits - Fifth Edition Sedra/Smith

70 sedr42021_p03003a.jpg Figure P3.3 Microelectronic Circuits - Fifth Edition Sedra/Smith

71 sedr42021_p03004a.jpg Figure P3.4 (Continued)
Microelectronic Circuits - Fifth Edition Sedra/Smith

72 sedr42021_p03004g.jpg Figure P3.4 (Continued)
Microelectronic Circuits - Fifth Edition Sedra/Smith

73 sedr42021_p03005.jpg Figure P3.5 Microelectronic Circuits - Fifth Edition Sedra/Smith

74 sedr42021_p03006a.jpg Figure P3.6 Microelectronic Circuits - Fifth Edition Sedra/Smith

75 sedr42021_p03009a.jpg Figure P3.9 Microelectronic Circuits - Fifth Edition Sedra/Smith

76 sedr42021_p03010a.jpg Figure P3.10 Microelectronic Circuits - Fifth Edition Sedra/Smith

77 sedr42021_p03016.jpg Figure P3.16 Microelectronic Circuits - Fifth Edition Sedra/Smith

78 sedr42021_p03023.jpg Figure P3.23 Microelectronic Circuits - Fifth Edition Sedra/Smith

79 sedr42021_p03025.jpg Figure P3.25 Microelectronic Circuits - Fifth Edition Sedra/Smith

80 sedr42021_p03026.jpg Figure P3.26 Microelectronic Circuits - Fifth Edition Sedra/Smith

81 sedr42021_p03028.jpg Figure P3.28 Microelectronic Circuits - Fifth Edition Sedra/Smith

82 sedr42021_p03054.jpg Figure P3.54 Microelectronic Circuits - Fifth Edition Sedra/Smith

83 sedr42021_p03056.jpg Figure P3.56 Microelectronic Circuits - Fifth Edition Sedra/Smith

84 sedr42021_p03057.jpg Figure P3.57 Microelectronic Circuits - Fifth Edition Sedra/Smith

85 sedr42021_p03058.jpg Figure P3.58 Microelectronic Circuits - Fifth Edition Sedra/Smith

86 sedr42021_p03059.jpg Figure P3.59 Microelectronic Circuits - Fifth Edition Sedra/Smith

87 sedr42021_p03063.jpg Figure P3.63 Microelectronic Circuits - Fifth Edition Sedra/Smith

88 sedr42021_p03082.jpg Figure P3.82 Microelectronic Circuits - Fifth Edition Sedra/Smith

89 sedr42021_p03091.jpg Figure P3.91 Microelectronic Circuits - Fifth Edition Sedra/Smith

90 sedr42021_p03092.jpg Figure P3.92 Microelectronic Circuits - Fifth Edition Sedra/Smith

91 sedr42021_p03093a.jpg Figure P3.93 Microelectronic Circuits - Fifth Edition Sedra/Smith

92 sedr42021_p03097.jpg Figure P3.97 Microelectronic Circuits - Fifth Edition Sedra/Smith

93 sedr42021_p03098.jpg Figure P3.98 Microelectronic Circuits - Fifth Edition Sedra/Smith

94 sedr42021_p03102.jpg Figure P3.102 Microelectronic Circuits - Fifth Edition Sedra/Smith

95 sedr42021_p03103.jpg Figure P3.103 Microelectronic Circuits - Fifth Edition Sedra/Smith

96 sedr42021_p03105.jpg Figure P3.105 Microelectronic Circuits - Fifth Edition Sedra/Smith

97 sedr42021_p03108.jpg Figure P3.108 Microelectronic Circuits - Fifth Edition Sedra/Smith


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