Diode application presentationnnnnnnnnnn

Diode presentation

1. CHAPTER 17
DIODES AND APPLICATIONS

2. Typical Diode package

3. Diode symbol

4. Diode Approximations
The ideal diode model

5. การป้อนไฟให้ Diode
Forward bias:
ให้ศักย์ไฟฟ้าด้าน Anode ( P ) สูงกว่า
Cathode ( N )
V
F> V
B (V
B(Si ) = 0.7 V;V
B(Ge
) = 0.3 V )
ป้อนไฟให้กระแสไหลในทิศตามลูกศร ของ

6. Diode Approximations
The complex diode model

7. DIODE CHARACTERISTICS
Diode Characteristic
Curve
Reverse bias
As the voltage (V
R)
increases to the
left, the current
remains near zero
until the
breakdown voltage
(V
BR) is reached
When breakdown
occurs, there is a
large reverse
current that can
destroy the diode

8. การป้อนไฟให้ Diode
Reverse bias:
ให้ศักย์ไฟฟ้าด้าน Anode ( P ) ต ่ากว่า
Kathode ( N )
ป้อนไฟให้กระแสไหลในทิศย้อนลูกศรของ
สัญลักษณ์ไดโอด
Diode จะท าตัวเหมือน switch เปิดท าให้
กระแสผ่านไม่ได้

9. Breakdown Voltage
(V
BR)
Reverse biasสูงมากจนกระทั่ง
Depletion region ขยายจนเต็มพื้นที่ Nและ P
Avalanche Effect
Free e
-
ฝั่ง P มีพลังงานสูงมากจนกระทั่ง ชน valence e
-
ใน P กลายเป็น Free e
-
ท าให้จ านวน Free e
-
เกิดเป็นจ านวนเท่าทวีคูณ( rapid
multiplication )
ท าให้เกิด Free e
-
ในฝั่ง P จ านวนมาก ไหลผ่าน
รอยต่อได้
กลายเป็นกระแสไหลในทิศย้อนกลับ

10. Diode Testing
Working diode
Forward bias:
Voltmeter: 0.7 v
Reverse bias:
Voltmeter: 2.5 –3.5 v
(internal meter voltage)
Open diode
Forward & Reverse bias
Voltmeter: 2.5-3.5 v
Ohm meter: High resistance
Shorted diode
Forward & Reverse bias
Voltmenter: 0 v
Ohm meter: Low resistance

11. การใช้งาน diode
ก าหนดทิศการไหลของกระแสในวงจร
ตัวอย่างวงจรที่ใช้งาน diode
วงจร rectifier ใน DC Power Supply
กระแสสลับ (AC) 2 ขั้ว (+/-) ให้เป็น กระแสตรง (
DC)(ขั้วเดียว)
วงจร Diode Limiter (จ ากัดความต่างศักย์
ของสัญญาณ AC)
วงจร Diode Clamper (ยกระดับความต่าง
ศักย์ของสัญญาณ AC)

12. Basic DC power supply
The dc power supply converts the standard
220 V,50 Hz into a constant dc voltage
They consist of three parts : Rectifier, Filter,
and Regulator
The dc voltage produced by a power supply is
used to power all types of electronic circuits,
such as television receivers, stereo systems,
VCRs, CD player

13. Power supply
Figure 17-1

14. The Half-Wave Rectifier
Figure 17-2
Average Value of
the Half-wave
output voltage
V
AVG=V
p (out)/ 

15. Effect of Diode Barrier Potential on
Half-Wave Rectifier Output Voltage
During the positive half-cycle, the input
voltage must overcome the barrier
potentialbefore the diode becomes
forward-biased
V
p(out)=V
p (in)-0.7 V
Figure 17-5

16. Peak Inverse Voltage (PIV)
The maximum value of reverse voltage,
sometimes designated as PIV, occurs at the
peak of each negativealternation of the input
cycle when the diode is reverse-biased
Figure 17-7

17. The full-wave rectifier is the most commonly used
type in dc power supplies
allowing unidirectional current to the load during
the entire input cycle differ from the half-wave
rectifier that allows only during one-half of the
cycle
FULL-WAVE RECTIFIERS
Figure 17-9
Average Value of the Full-wave rectified output voltage
V
AVG= 2V
p (out)/ 

18. Center-Tapped Full-Wave Rectifier
Using two diode connected to the secondary of
a center-tapped transformer
At the positive half-cycle
Forward-biases the upper diode D1
Reverse-biases the upper diode D2
At the negative half-cycle
Reverse-biases the upper diode D1
Forward-biases the upper diode D2

19. Center-Tapped Full-Wave Rectifier

20. Effect of the Turn Ratio on Full-Wave
Output Rectifier
If the turn ratio of the transformer is
1:1, the output of the rectifier is equal
to ½ of the input voltage V
p
Owing to the voltage input is
approximately equal to the output
voltage, we must use the step-up
transformer

21. Peak Inverse Voltage (full-wave
rectifier)(sec)p
(sec)p
(sec)p
)out(p
(sec)p
(sec)p(sec)p
2D
V2
2
V
2
V
V
V
2
V
2
V
V











 )out(p(sec)p
V2VPIV 

22. Full-Wave Bridge Rectifier

23. Bridge Output Voltage)out(p(sec)p
VVPIV 

24. POWER SUPPLY FILTER AND
REGULATORS
After passed the rectifier, the output of the
power supply is filtered for reduce the
ripple, on the other hand, for make an
output smoothly
Capacitor-Input filter
Ripple Voltage
The voltage which change due to charging and
discharge of the capacitor is called “ripple voltage”

25. Ripple Voltages for half-wave and
full-wave

26. Ripple Factor (r)
Ripple factor is the ratio of theV
r to V
DC,
expressed as :%100
V
V
r
DC
r

NOTE: the frequency in the full-wave rectifier is
twice of the half-wave rectifier

27. Surge Current in the Capacitor-Input
Filter

28. IC Regulators
An integrated circuit regulator is a device that
is connected to the output of a filtered
rectifier and maintains a constant output
voltage
The capacitor-input filter reduces the input
ripple to the regulator to an acceptable level
and it is combined in IC regulator.
The most IC regulators have three terminal
Input terminal
Output terminal
Reference terminal

29. IC Regulators

30. Basic regulated power supply

31. Percent Regulation
Line regulation
Specifies how much change occurs in the output
voltage for a given change in the input voltage
Load regulation
Specifies how much change occurs in the output
voltage over a certain range of load current value
∆V
OUT
∆V
IN%100
Line regulation =
V
NL-V
FL
V
FL%100
Load regulation =

32. Diode Limiter
Diode Limiters
Diode limiters (clipper) cut off above or below specified levelsin
LS
L
out V
RR
R
V











33. Diode Limiting and Clamping
Circuits
Diode Limiters
Adjustment of the limiting level

34. Diode Clampers
Diode clamper known as a dc restorer
Add a dc level to an ac signal

35. Diode Clampers

36. ชนิดของ Diode
Regular diode
Zener diode
Varactor diode
Light-Emitting diode (LED)
Photo diode

37. ZENER DIODES
The zener diode is a
silicon pn junction device
and operate in the
reverse breakdown region
symbol

38. Zener Breakdown (V
z)
Two types of reverse breakdown in
a diode
Avalanche
also occurs in the rectifier diode
(regular diode)
Zener
Occurs in a zener diodeat low reverse
voltages
NOTE : Zeners with breakdown voltage of 1.8 to
200 Vare commercially available

39. Breakdown CharacteristicZMzenerZK III 
Regulator: ตัวคงค่าความต่างศักย์

40. Zener Equivalent Circuit
Regulator: ตัวคงค่าความต่างศักย์

41. Zener diode impedance
The ratio of ∆V
zto ∆I
zis the zener
diode impedance
Normally, Z
Zis specified at I
ZT
Z
Z is approximately constant over the
full range of reverse-current values
∆V
Z
∆I
Z
Z
z =

42. Zener Voltage Regulation
Zener diodes can be
used for voltage
regulation in
noncritical low-current
applicationsZMzenerZK III 

43. As the input voltage varies, the zener
diode hole the constant voltage across
the output terminals
Zener Voltage Regulation

44. Zener Regulation with a Varying Load
The zener diode maintains a constant voltage
across R
Las long as the zener current is
greater than I
ZKand less than I
ZM, this
process is calledload regulation

45. VARACTOR DIODES
A varactor is basically a reverse-biasedpn
junction that utilizes the inherent capacitance
of the depletion region
The depletion region acts as a capacitor
dielectricd
A
C



46. VARACTOR DIODESd
A
C



47. VARACTOR DIODES

48. VARACTOR DIODE APPLICATIONSLC
f
r
2
1


49. LEDs and PHOTODIODES
There are two types of optoelectronic
devices
The Light Emitting Diode (LED)
The photodiode (light detector)

50. The Light Emitting Diode (LED)
When the device is forward-biased,
electrons across the pnjunction from the n-
type material and recombine with the holes
in the p-type material
When recombinationtakes place, the
recombining electrons release energy in the
form of heat and light

51. The Light Emitting Diode (LED)
The semiconductive materials used in LEDs are
gallium arsenide(GaAs), galium arsenide
phosphide (GaAsP), and Gallium phosphide (GaP)
Silicon and Germaniumare not used because they
are very poor at producing light
GaAsLEDs emit infrared (IR)radiation
GaAsPproduces either red or yellowvisible light
GaPemits red or greenvisible light

52. The Light Emitting Diode (LED)
symbol
electroluminescence

53. The Light Emitting Diode (LED)

54. The Light Emitting Diode (LED)
Applications

55. The Photodiode
The photodiode is a pnjunction device
that operates in reverse bias

56. The Photodiode

57. The Photodiode operation

58. The Photodiode Applications

59. The diode data sheet

60. TROUBLESHOOTING