The document discusses different types of diodes and their applications. It covers half-wave and full-wave rectifiers used in power supplies to convert AC to DC. It also discusses zener diodes, which regulate voltage, and varactor diodes, which are used in voltage-controlled oscillators. Finally, it covers light emitting diodes and photodiodes, their operating principles, and applications.
2. HALF-WAVE RECTIFIERS
⢠The basic DC power supply
â The dc power supply converts the standard
220 V,50 Hz into a constant dc voltage
â They consist of three parts : Rectifier, Filter,
and Regulator
â 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
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) / ď°
8. Center-Tapped Full-Wave Rectifier
⢠Using two diode connected to the secondary of a center-
tapped transformer
â At the positive half-cycle
⢠Forward-biases the upper diode D1
⢠Reverse-biases the upper diode D2
â 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
ď˝
ď˝
ď˝
ďˇ
ďˇ
ď¸
ďś
ď§
ď§
ď¨
ďŚ
ď
ď
ď˝
)
out
(
p
(sec)
p V
2
V
PIV ď˝
ď˝
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
â Capacitor-Input filter
â Ripple Voltage
⢠The voltage which change due to charging and
discharge of the capacitor is called âripple voltageâ
15. Ripple Factor (r)
⢠Ripple factor is the
ratio of the Vr to VDC,
expressed as :
%
100
V
V
r
DC
r
ď´
ď˝
NOTE: the frequency in the full-wave rectifier is
twice of the half-wave rectifier
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
â Input terminal
â Output terminal
â Reference terminal
21. Percent Regulation
⢠Line regulation
â Specifies how much change occurs in the
output voltage for a given change in the input
voltage
⢠Load regulation
â Specifies how much change occurs in the
output voltage over a certain range of load
current value
âVOUT
âVIN
%
100
ď´
Line regulation =
VNL- VFL
VFL
%
100
ď´
Load regulation =
22. Diode Limiting and Clamping
Circuits
⢠Diode Limiters
â Diode limiters (clipper) cut off above or below
specified levels
in
L
S
L
out V
R
R
R
V ďˇ
ďˇ
ď¸
ďś
ď§
ď§
ď¨
ďŚ
ďŤ
ď˝
23. Diode Limiting and Clamping
Circuits
⢠Diode Limiters
â Adjustment of the limiting level
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
â Avalanche
⢠also occures in the rectifier diode
â 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 âVz to âIz is the zener diode
impedance
⢠Normally, ZZ is specified at IZT
⢠ZZ is approximately constant over the full
range of reverse-current values
âVOUT
âVIN
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
â Specifies how much change occurs in the
output voltage for a given change in the input
voltage
⢠Load regulation
â 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
ďĽ
ďĽ
ď˝
ď˝
39. LEDs and PHOTODIODES
⢠There are two types of optoelectronic
devices
â The Light Emitting Diode (LED)
â 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