dien-tu-tuong-tu_pham-nguyen-thanh-loan_chapter-1-_diodes-and-applications - [cuuduongthancong.com] (1).pdf

hhjjkhjkhkjhkjhjkhkjhj

1. Electronics Circuits I
Chapter 1: Diodes and applications
Dr. Pham Nguyen Thanh Loan
Ha Noi, 21/8/2013

2. Chapter 1: Diode & applications
Contents
Diode – Structure, operation and equivalent circuit
Rectifiers circuits
Limiters circuits
Double voltage and so on
Zener diode and its applications

3. Diode structure
PN Junction
Depletion region: no carriers
Ion located at the interfaces with P/N  barrier voltage V
D  drift
current I
S (i
drift)
Diffusion phenomenon: flow of charges from high concentration
region to lower concentration region  I
D (i
diff)
Equilibrium of PN junction: Is + I
D = 0

4. PN junction and its symbol: Diode
Kathode (K)
Anode (A)
Anode (A) Kathode (K)

5. Model of ideal diode
Two terminals
Current ON in one direction
V
D = 0V
FORWARD BIAS
I
D ↑ very fast
REVERSE BIAS
I
D ≈ 0

6. Model of practical diode (VD ≠ 0)
FORWARD BIAS: applied
voltage > V
D
V
D ≈ 0.7V ( Si)
V
D ≈ 0.3V ( Ge)
 Voltage drop on diode = V
D
REVERSE BIAS:
Leakage current I
S ≈ 0
 Open circuit

7. PRACTICAL Diode

8. PRACTICAL Diode

9. PRACTICAL Diode (VD ≠ 0)
0.3(Ge) 0.7(Si)
(Ge)
(Si)
V
D(V)
I
D(mA)
I
s(Si)=10nA
I
s=reverse saturation current
I
s(Ge)

10. PRACTICAL Diode

11. PRACTICAL Diode - multimeter

12. PRACTICAL Diode - multimeter

13. Large signal model

14. Small signal model

15. Applications
Rectifiers
Half wave
Full wave
Wien bridge
Using capacitor (filters)
Limiters
Double voltage

16. Rectifiers

17. Half wave

18. Half wave: 1
st
half positive periode
Diode: OFF, I
D=0
V
out = 0

Diode: ON
V
out = V
in - V
D

19. Half wave with transformer
 Example: Analyze the following circuit

20. Fullwave rectifier
Waveform of input and output signal

21. Fullwave rectifier: schematic

22. Fullwave rectifier: operation

23. NOTES: CURRENT
flows through load
resistor following a
unique direction and
can’t be reversed
Fullwave rectifier: operation

24. Determine PIV
 PIV = V
P(sec) + 0.7V

25. Ex: Determine PIV

26. Bridge rectifier

27. Bridge rectifier

28. PIV = V
P(OUT) + 0.7V
Bridge rectifier

29. Bridge rectifier

30. Filters

31. Roles of Capacitor

32. Input: Sinusoidal waveform, imput f: 60Hz
Output frequency

33. Ripples observed on output signals
Same filter cap, load and input signal
Ripple consideration

34. A supply voltage
Used in most electronics devices
Simple, cheap and easy to construct

35. output from 1.25 to 6.5V
A supply voltage –

36. Limiters

37. Different operation of diodes
Input and output waveforms

38. Similar Zener diode operation
Input and output waveforms

39. Limiters associated with voltage divider
Ex: Analyze this circuit

40. Clamp circuit
Displace the DC level at output
Consisting of:
 Capacitor
 Diode
 Resistors
 battery
Resistor and capacitor are chosen how to
guarantee a τ = RC big enough so that the
discharge time of capacitor is still higher than the
reverse period of diode

41. 1
st
half period (+)





Clamp operation
+
R
Vo
-
+
-
Vi
C
• 0 T/2: Diode ON (short circuit)
• C charges to level V
i
• V
o= 0 V
2
nd
half period (-)

• T/2 T: Diode OFF (open circuit),
Kirchoff Voltage Law:
- V- V- V
o = 0 and
 V
o = -2V

+
R
Vo
-
+
-
V
C
Vo
-
+
V

42. Results from Circuit Maker

43. Results from Circuit Maker

44. Positive Clamp circuit

45. Negative clamp circuit

46. Negative clamp circuit

47. voltage doubler

48. voltage doubler

49. Triple voltage

50. Mạch nhân bốn

51. Supply voltage

52. Signals at different nodes

53. Signals at different nodes

54. Homeworks
Chapter 2: 1, 5, 6, 10, 11, 15, 21, 23, 24, 27, 30, 34,
37, 42, 47, 49, 52