Pabna University of Science and Technology
Department of
Electrical and Electronic Engineering
Faculty of Engineering and Technology
Presentation on: “Exploring Diodes: Fundamentals & Applications’’
Course Code: EEE-2210
Course Title: Electrical Machine-II
Presentation Date: 10-12-2024
TEAM INTRODUCTION
TEAM NAME: TEAM RECTIFIER
Team Members:
• Md. Shoron Sheikh (220222)
• Md. Musaddiqur Rahman (220223)
• Taiful Islam Khan Rongon (220224)
• Md. Sojib Miah (220225)
• Md. Zaber (220226)
• Md.Yasir Ahmed (220227)
• Md. Zilhajur Rahman (220228)
• Shuvongkor Sarkar (220229)
• Mst. Farzana Afrin (220230)
• Sakib Islam (200232)
What is Diode?
A diode is a two-terminal electronic component that conducts
current primarily in one direction. It has low (ideally zero)
resistance in one direction and high (ideally infinite)
resistance in the other.
While most diodes today are made of silicone, historically,
there were two types: vacuum tube and semiconductor.
Vacuum tube diodes are now rarely used.
Vacuum Diode Construction
It includes two electrodes (an anode
and a cathode) and sometimes a hitter.
All of these are enclosed within an
empty envelope of glass.
Vacuum Diode Working Principle
The vacuum diode works on the thermionic emission
principle. Once a filament heats the cathode terminal, it
emits electrons and these electrons will be attracted by
the anode. If the positive voltage is given at the anode
terminal is not enough then it cannot attract the electrons
generated from the cathode because of the hot filament.
There could be three cases:
Case1: Forward Voltage
Once the voltage supply is provided to the
vacuum diode in such a way that the anode
terminal of the diode is given to a positive
terminal whereas the cathode is given to a
negative terminal then free electrons within the
vacuum obtain sufficient kinetic energy to
arrive at the anode.
Case2: Reverse Voltage
Here anode terminal of the diode is
connected to the negative terminal whereas
the cathode is connected to the positive
terminal. So, the anode terminal is charged
negatively & free electrons generated from
the cathode are also charged negatively.
Thus, the anode repels the emitted electrons
from the cathode. Consequently, there is no
flow of current within the vacuum diode.
Case3: No Voltage
Once no voltage is given to the
vacuum diode, then the anode
performs like neutral. So it neither
repels nor attracts the free electrons
generated from the cathode. So, there
is no flow of current within the vacuum
diode.
Semiconductor Diode Construction
A semiconductor diode has two layers. One layer is made
of a P-type semiconductor layer and the second layer is
made of an N-type semiconductor layer. Hence it is also
known as PN Junction Diode.
A diode has two terminals; one terminal is taken from the
P-type layer and it is known as Anode. The second terminal
is taken from the N-type material and it is known as
Cathode.
Working of Diode
In the N-type region, electrons are the majority charge carriers and
holes are minority charge carriers. In the P-type region, the holes
are majority charge carrier and the electrons are minority charge
carriers. Near to junction electrons of N-type and holes of P-type
recombine and forms a depletion region. This depletion layer acts
similar to insulator.
On the basis of applied voltage there could be two cases:
1. When anode terminal of diode is connected with a negative
terminal and cathode is connected with the positive terminal of
a battery, the diode is said to be connected in reverse bias.
2. when anode terminal is connected with a positive terminal and
cathode is connected with the negative terminal of the battery,
the diode is said to be connected in forward bias.
Operation of Diode in Reverse Bias Condition:
In this condition, free electrons diffusing into the P-type regions and
recombine with holes. It will create negative ions. Similarly, holes
diffuse into the N-type region and recombine with electrons. So,
width of depletion region increases and the diode acts as a
insulator.
P-type N-type
Operation of Diode in Forward Bias Condition:
In the forward bias conditions, the width of the depletion region is
very small. If we increase the voltage more than forward breakover
voltage, the majority charge carrier gets enough energy to cross the
depletion region. So the diode acts as a short circuit.
For silicon forward breakover voltage is 0.7V and for germanium
forward breakover voltage is 0.3V.
VI-Characteristics curve of Semiconductor Diode
How diode converts alternating
current into direct current?
Half-Wave Rectifier Circuit
It is a circuit in which only a single diode rectifier is used
to conduct ac supply current in one direction through a
load during a half-cycle and stops to conduct during next
half-cycle.
Full-wave rectifier
A full wave rectifier converts the entire AC waveform into
pulsating DC, utilizing both halves of the input cycle.
A special Semiconductor Diodes
Zener diode
A Zener diode can be defined as a heavily doped
semiconductor device that is designed to operate the
electric circuit in the reverse direction. Its main objective is
to regulate voltage.
Zener diode as voltage regulator
It is specifically designed to work in reverse-biased conditions but
when it is put under a forward-biased condition it works as a single
diode. When the reverse voltage is applied to it then a voltage
remains consistent even for a wide range of currents flowing
through it. Due to this characteristic, it is also used as a voltage
regulator in DC circuits.
Conclusion
Diodes are fundamental semiconductor devices that
allow current to flow in one direction and block it in
the opposite direction.
Different types of diodes, such as Zener, Tunnel, and
PN junction diodes, serve specific purposes like
voltage regulation, high-frequency operation, and
rectification.
They play a vital role in modern electronics, powering
applications in signal processing, voltage regulation,
and protection circuits.
Thank you all for
your attention.
