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CHAPTER 17
DIODES AND APPLICATIONS
HALF-WAVE RECTIFIERS
• The 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
Power supply
Figure 17-1
The Half-Wave Rectifier
Figure 17-2 Average Value of
the Half-wave
output voltage
VAVG=Vp (out) / 
Effect of Diode Barrier Potential on
Half-Wave Rectifier Output Voltage
• During the positive half-cycle, the input
voltage must overcome the barrier potential
before the diode becomes forward-biased
Vp (out) =Vp (in) - 0.7 V
Figure 17-5
Peak Inverse Voltage (PIV)
• The maximum value of reverse voltage,
sometimes designated as PIV, occurs at
the peak of each negative alternation of
the input cycle when the diode is reverse-
biased
Figure 17-7
• 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
VAVG= 2Vp (out) / 
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
Center-Tapped Full-Wave Rectifier
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 Vp
• Owing to the voltage input is
approximately equal to the output voltage,
we must use the step-up transformer
Peak Inverse Voltage (full-wave
rectifier)
(sec)
p
(sec)
p
(sec)
p
)
out
(
p
(sec)
p
(sec)
p
(sec)
p
2
D
V
2
2
V
2
V
V
V
2
V
2
V
V














)
out
(
p
(sec)
p V
2
V
PIV 

Full-Wave Bridge Rectifier
Bridge Output Voltage
)
out
(
p
(sec)
p V
V
PIV 

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”
Ripple Factor (r)
• Ripple factor is the
ratio of the Vr to VDC,
expressed as :
%
100
V
V
r
DC
r


NOTE: the frequency in the full-wave rectifier is
twice of the half-wave rectifier
Ripple Voltages for half-wave and
full-wave
Surge Current in the Capacitor-
Input Filter
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
IC Regulators
Basic regulated power supply
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
∆VOUT
∆VIN
%
100

Line regulation =
VNL- VFL
VFL
%
100

Load regulation =
Diode Limiting and Clamping
Circuits
• Diode Limiters
– Diode limiters (clipper) cut off above or below
specified levels
in
L
S
L
out V
R
R
R
V 









Diode Limiting and Clamping
Circuits
• Diode Limiters
– Adjustment of the limiting level
Diode Clampers
• Diode clamper known as a dc restorer
– Add a dc level to an ac signal
Diode Clampers
ZENER DIODES
• The zener diode is a
silicon pn junction device
and operate in the
reverse breakdown
region
symbol
Zener Breakdown (Vz)
• Two types of reverse breakdown in a
zener diode
– Avalanche
• also occures in the rectifier diode
– Zener
• Occurs in a zener diode at low reverse voltages
NOTE : Zeners with breakdown voltage of 1.8 to
200 V are commercially available
Breakdown Characteristic
Zener Equivalent Circuit
Zener diode impedance
• The ration of ∆Vz to ∆Iz is the zener diode
impedance
• Normally, ZZ is specified at IZT
• ZZ is approximately constant over the full
range of reverse-current values
∆VOUT
∆VIN
Zz =
Zener Voltage Regulation
• Zener diodes can be used for voltage
regulation in noncritical low-current
applications
• As the input voltage varies, the zener
diode hole the constant voltage across the
output terminals
Zener Voltage Regulation
Zener Regulation with a Varying
Load
• The zener diode maintains a constant
voltage across RL as long as the zener
current is greater than IZK and less than
IZM, this process is called load regulation
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
VARACTOR DIODES
• A varactor is basically a reverse-biased pn
junction that utilizes the inherent
capacitance of the depletion region
• The depletion region acts as a capacitor
dielectric
dielectric constant
A
C
d




VARACTOR DIODES
VARACTOR DIODES
VARACTOR DIODE APPLICATIONS
LC
fr

2
1

LEDs and PHOTODIODES
• There are two types of optoelectronic
devices
– The Light Emitting Diode (LED)
– The photodiode (light detector)
The Light Emitting Diode (LED)
• When the device is forward-biased,
electrons across the pn junction from the
n-type material and recombine with the
holes in the p-type material
• When recombination takes place, the
recombining electrons release energy in
the form of heat and light
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 Germanium are not used because
they are very poor at producing light
• GaAs LEDs emit infrared (IR) radiation
• GaAsP produces either red or yellow visible light
• GaP emits red or green visible light
The Light Emitting Diode (LED)
symbol
electroluminescence
The Light Emitting Diode (LED)
The Light Emitting Diode (LED)
Applications
The Photodiode
• The photodiode is a pn junction device
that operates in reverse bias
The Photodiode
The Photodiode operation
The Photodiode Applications
The diode data sheet
TROUBLESHOOTING
Homework
• Basic problems
– 1, 6, 12,16
12
16

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diode.ppt

  • 1. CHAPTER 17 DIODES AND APPLICATIONS
  • 2. HALF-WAVE RECTIFIERS • The 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
  • 4. The Half-Wave Rectifier Figure 17-2 Average Value of the Half-wave output voltage VAVG=Vp (out) / 
  • 5. Effect of Diode Barrier Potential on Half-Wave Rectifier Output Voltage • During the positive half-cycle, the input voltage must overcome the barrier potential before the diode becomes forward-biased Vp (out) =Vp (in) - 0.7 V Figure 17-5
  • 6. Peak Inverse Voltage (PIV) • The maximum value of reverse voltage, sometimes designated as PIV, occurs at the peak of each negative alternation of the input cycle when the diode is reverse- biased Figure 17-7
  • 7. • 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 VAVG= 2Vp (out) / 
  • 8. 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
  • 10. 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 Vp • Owing to the voltage input is approximately equal to the output voltage, we must use the step-up transformer
  • 11. Peak Inverse Voltage (full-wave rectifier) (sec) p (sec) p (sec) p ) out ( p (sec) p (sec) p (sec) p 2 D V 2 2 V 2 V V V 2 V 2 V V               ) out ( p (sec) p V 2 V PIV  
  • 14. 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”
  • 15. Ripple Factor (r) • Ripple factor is the ratio of the Vr to VDC, expressed as : % 100 V V r DC r   NOTE: the frequency in the full-wave rectifier is twice of the half-wave rectifier
  • 16. Ripple Voltages for half-wave and full-wave
  • 17. Surge Current in the Capacitor- Input Filter
  • 18. 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
  • 21. 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 ∆VOUT ∆VIN % 100  Line regulation = VNL- VFL VFL % 100  Load regulation =
  • 22. Diode Limiting and Clamping Circuits • Diode Limiters – Diode limiters (clipper) cut off above or below specified levels in L S L out V R R R V          
  • 23. Diode Limiting and Clamping Circuits • Diode Limiters – Adjustment of the limiting level
  • 24. Diode Clampers • Diode clamper known as a dc restorer – Add a dc level to an ac signal
  • 26. ZENER DIODES • The zener diode is a silicon pn junction device and operate in the reverse breakdown region symbol
  • 27. Zener Breakdown (Vz) • Two types of reverse breakdown in a zener diode – Avalanche • also occures in the rectifier diode – Zener • Occurs in a zener diode at low reverse voltages NOTE : Zeners with breakdown voltage of 1.8 to 200 V are commercially available
  • 30. Zener diode impedance • The ration of ∆Vz to ∆Iz is the zener diode impedance • Normally, ZZ is specified at IZT • ZZ is approximately constant over the full range of reverse-current values ∆VOUT ∆VIN Zz =
  • 31. Zener Voltage Regulation • Zener diodes can be used for voltage regulation in noncritical low-current applications
  • 32. • As the input voltage varies, the zener diode hole the constant voltage across the output terminals Zener Voltage Regulation
  • 33. Zener Regulation with a Varying Load • The zener diode maintains a constant voltage across RL as long as the zener current is greater than IZK and less than IZM, this process is called load regulation
  • 34. 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
  • 35. VARACTOR DIODES • A varactor is basically a reverse-biased pn junction that utilizes the inherent capacitance of the depletion region • The depletion region acts as a capacitor dielectric dielectric constant A C d    
  • 39. LEDs and PHOTODIODES • There are two types of optoelectronic devices – The Light Emitting Diode (LED) – The photodiode (light detector)
  • 40. The Light Emitting Diode (LED) • When the device is forward-biased, electrons across the pn junction from the n-type material and recombine with the holes in the p-type material • When recombination takes place, the recombining electrons release energy in the form of heat and light
  • 41. 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 Germanium are not used because they are very poor at producing light • GaAs LEDs emit infrared (IR) radiation • GaAsP produces either red or yellow visible light • GaP emits red or green visible light
  • 42. The Light Emitting Diode (LED) symbol electroluminescence
  • 43. The Light Emitting Diode (LED)
  • 44. The Light Emitting Diode (LED) Applications
  • 45. The Photodiode • The photodiode is a pn junction device that operates in reverse bias
  • 49. The diode data sheet
  • 51. Homework • Basic problems – 1, 6, 12,16 12 16