1. Diodes Introduction Textbook CD
Textbook CD

2. Introduction

3. The Ideal Diode
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.

4. Rectifier Circuit Input waveform. Rectifier circuit
Equivalent circuit when v1 > 0
Equivalent circuit when v1  0
Output waveform.

5. Rectifier Circuit
Example 3.1

6. Rectifier Circuit
Example 3.2

7. Terminal Characteristics of Junction Diodes – Forward Region
Example 3.3

8. Terminal Characteristics of Junction Diodes – Reverse-Bias Region
Exercise 3.9

9. Rectifier Circuit
Exercises 3.4 and 3.5

10. Diode – i-v Characteristic
The i-v characteristic of a silicon junction diode.

11. Diode – i-v Characteristic
Thermal Voltage
25mV at room temp.
ln = 2.3 log
The diode i-v relationship with some scales expanded and others compressed in order to reveal details.

12. Diode – i-v Characteristic Exercise 3.6
Consider a silicon diode with n=1.5. Find the change in voltage if current changes from 0.1 mA to 10 mA.

13. Diode – i-v Characteristic
A diode for which the forward voltage drop is 0.7 V at 1 mA and for which n=1 is operated at 0.5 V. What is the value of the current?

14. Diode – Simplified Physical Structure
Simplified physical structure of the junction diode. (Actual geometries are given on Appendix A.)

15. Diode – Semiconductor Physics
The semiconductor diode is what is called a pn junction and is shown in the figure on the right
Both the p and the n sections are part of the same crystal of silicon. At room temp., some
of the covalent bonds in silicon break and electrons are attracted to other atoms. These moving
electrons leave a hole behind that is filled by another electron, thus continuing the cycle. In
thermal equilibrium the concentration of holes (p) and the concentration of free electrons (n) are
equal to each other and to ni which is the number of holes or free electrons in silicon at a given temp. Study of semiconductor physics yields the following equation for the free electrons.

16. Diode – Semiconductor Physics

17. Diode – Semiconductor Physics

18. Diode – Semiconductor Physics

19. Diode – Semiconductor Physics

20. Diode – Semiconductor Physics

21. Diode – Semiconductor Physics

22. Diode –Physical Structure

23. Diode –Physical Structure

24. Diode –Physical Structure

25. Diode –Physical Structure

26. Diode –Physical Structure
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.

27. Diode –Physical Structure

28. Diode – Characteristic
Lessons In Electric Circuits copyright (C) Tony R. Kuphaldt

29. Diode – Characteristic
Lessons In Electric Circuits copyright (C) Tony R. Kuphaldt

30. Diode – Characteristic
Lessons In Electric Circuits copyright (C) Tony R. Kuphaldt

31. Diode – Characteristic
Lessons In Electric Circuits copyright (C) Tony R. Kuphaldt

32. Diode – Applications
Lessons In Electric Circuits copyright (C) Tony R. Kuphaldt

33. Diode – Applications
Lessons In Electric Circuits copyright (C) Tony R. Kuphaldt

34. Diode – Applications

35. Diode – Applications

36. Diode – Applications

37. Diode – Applications

38. Analysis of Diode Circuits
A simple diode circuit.

39. Graphical Analysis
Graphical analysis of the circuit above

40. Iterative Analysis
Example 3.4

41. Simplified Diode Models
Approximating the diode forward characteristic with two straight lines.

42. Simplified Diode Models Example 3.5
Piecewise-linear model of the diode forward characteristic and its equivalent circuit representation.

43. The Constant-Voltage Drop Model
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.

44. The Constant-Voltage Drop Model
The constant-voltage-drop model of the diode forward characteristic and its equivalent circuit representation.

45. The Small-Signal Model
Development of the diode small-signal model. Note that the numerical values shown are for a diode with n = 2.

46. The Small-Signal Model Example 3.6
Equivalent circuit model for the diode for small changes around bias point Q. The incremental resistance rd is the inverse of the slope of the tangent at Q, and VD0 is the intercept of the tangent on the vD axis.

47. The Small-Signal Model
The analysis of the circuit in (a), which contains both dc and signal quantities, can be performed by replacing the diode with the model of previous figure, as shown in (b). This allows separating the dc analysis [the circuit in (c)] from the signal analysis [the circuit in (d)].

48. Zener Diode - Characteristics
6.8 –V, 10mA
0.5W, 6.8-V, 70mA
Vz = Vzo + r2Iz
Vz > Vzo
Circuit symbol for a zener diode.
The diode i-v characteristic with the breakdown region shown in some detail.
Model for the zener diode.

49. Rectifier Circuits
Block diagram of a dc power supply.

50. Rectifier Circuits
(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.

51. Rectifier Circuits
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.

52. Rectifier Circuits PIV V  V s DO
The bridge rectifier: (a) circuit and (b) input and output waveforms.
PIV V  V s DO

53. With A Filter Capacitor
Rectifier Circuits
With A Filter Capacitor
Voltage and current waveforms in the peak rectifier circuit with CR  T. The diode is assumed ideal.

54. Rectifier Circuits
With A Filter Capacitor

55. Rectifier Circuits
With A Filter Capacitor

56. With A Filter Capacitor
Rectifier Circuits
With A Filter Capacitor
If Vp = 100 V
R = 10 K
Calculate the value of the capacitance C that will result in a peak-to-peak ripple
Vr of 5 V, the conduction angle and the average and peak values of the diode current.

57. The Spice Diode Model and Simulation Examples
The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers).
name parameter units default example
1 IS saturation current A 1.0E E-14 *
2 RS ohmic resistance Ohm *
3 N emission coefficient
4 TT transit-time sec 0 0.1Ns
5 CJO zero-bias junction capacitance F 0 2PF *
6 VJ junction potential V 1 0.6
7 M grading coefficient
8 EG activation energy eV Si
0.69 Sbd
0.67 Ge

58. The Spice Diode Model and Simulation Examples
The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers).
name parameter units default example a
9 XTI saturation-current temp. exp jn
2.0 Sbd
10 KF flicker noise coefficient - 0
11 AF flicker noise exponent - 1
12 FC coefficient for forward-bias - 0.5
depletion capacitance formula
13 BV reverse breakdown voltage V infinite
14 IBV current at breakdown voltage A 1.0E-3

59. The Spice Diode Model and Simulation Examples
PN Junction Diodes
Name Parameter Units Default
IS saturation current A 1.0E-14
N emission coefficient
BV reverse breakdown voltage V infinite
RS diode series resistance  0
CJO zero-bias junction capacitance F 0
VJ junction potential V 1
M grading coefficient

60. Limiting and Clamping Circuits
A variety of basic limiting circuits.