GOLDEN GATE COLLEGES
P. Prieto St., Batangas City
College of Engineering & Technology
Bachelor of Science in Electrical
Engineering
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR
INDUSTRIAL ELECTRONICS
Submitted to:
ENGR. JECSON ABANTE
Submitted by:
CAIBIGAN, JHON ZYRD C.
SEPTEMBER 2023
Diode
A diode is made up of two words i.e., “Di “means Two, and “Ode “means
Electrodes which means that a device or component has two electrodes. (i.e., cathode
and anode). A diode is an electronic device having a two-terminal unidirectional power
supply i.e., it has two terminals and allows the current to flow only in one direction.
Diodes are widely used in modern-day circuits to secure circuits from over-voltage and
they are also used to change AC current to DC current.
A diode is a device for controlling electrical currents so that they only flow the
desired way (the way the engineer wants them to.
A diode is defined as a two-terminal electronic component that only
conducts current in one direction (so long as it is operated within a specified voltage
level). An ideal diode will have zero resistance in one direction, and infinite resistance in
the reverse direction. Although in the real world, diodes can not achieve zero or infinite
resistance. Instead, a diode will have negligible resistance in one direction (to allow
current flow), and very high resistance in the reverse direction (to prevent current flow).
A diode is effectively like a valve for an electrical circuit.
Diodes are used in all kinds of electronic devices. Most diodes in use today are
semiconductor diodes. People often simply use the word diode when they are talking
about a semiconductor diode. A semiconductor is a material that electricity can travel
through, but not as well as when it travels through a stronger conductor like copper.
This kind of diode is kind of like a door for electricity to move through, but it only opens
one way.
Among the simplest kinds of this device are p-n junction diodes. Such diodes are
commonly made from the semiconductor silicon. Silicon doesn’t conduct very well on its
own, but its conductivity can be improved by adding other elements. Depending on what
you add to the silicon, it can become either what’s called a p-type material, which has a
positive charge, or an n-type material, which has a negative charge. To create the
diode, some p-type material and n-type material are put together. The p-type is the
anode, and the n-type is the cathode. At the junction, where the two materials meet,
they cancel each other out, and the area around the junction doesn’t have a charge.
The electrical current can’t cross it. If you add a positive electrical current to the positive
end and a negative one to the negative end, the junction gets smaller and electricity can
flow across the junction. But if you reverse that, the junction gets bigger and the current
can’t go across. So, electricity can only be conducted in one direction, and the diode is
created. Diodes are used to protect circuits by limiting the voltage and to also transform
AC into DC. Semiconductors like silicon and germanium are used to make the most of
the diodes. Even though they transmit current in a single direction, the way with which
they transmit differs. There are different kinds of diodes and each type has its own
applications.
List of Different types of Diodes
Diode Symbol
Light Emitting Diode (LED)
When an electric current between the electrodes passes through this diode, light
is produced. In other words, light is generated when a sufficient amount of forwarding
current passes through it. In many diodes, this light generated is not visible as there are
frequency levels that do not allow visibility. LEDs are available in different colours.
There are tricolour LEDs that can emit three colours at a time. Light colour depends on
the energy gap of the semiconductor used.
Laser Diode
It is a different type of diode as it produces coherent light. It is highly used in CD
drives, DVDs and laser devices. These are costly when compared to LEDs and are
cheaper when compared to other laser generators. Limited life is the only drawback of
these diodes.
Avalanche Diode
This diode belongs to a reverse bias type and operates using the avalanche
effect. When voltage drop is constant and is independent of current, the breakdown of
avalanche takes place. They exhibit high levels of sensitivity and hence are used for
photo detection.
Zener Diode
It is the most useful type of diode as it can provide a stable reference voltage.
These are operated in reverse bias and break down on the arrival of a certain voltage. If
current passing through the resistor is limited, a stable voltage is generated. Zener
diodes are widely used in power supplies to provide a reference voltage.
Schottky Diode
It has a lower forward voltage than other silicon PN junction diodes. The drop will
be seen where there is low current and at that stage, voltage ranges between 0.15 and
0.4 volts. These are constructed differently in order to obtain that performance. Schottky
diodes are highly used in rectifier applications.
Photodiode
A photo-diode can identify even a small amount of current flow resulting from the
light. These are very helpful in the detection of the light. This is a reverse bias diode and
used in solar cells and photometers. They are even used to generate electricity.
P-N Junction Diode
The P-N junction diode is also known as rectifier diodes. These diodes are used
for the rectification process and are made up of semiconductor material. The P-N
junction diode includes two layers of semiconductors. One layer of the semiconductor
material is doped with P-type material and the other layer with N-type material. The
combination of these both P and N-type layers form a junction known as the P-N
junction. Hence, the name P-N junction diode.
Applications and Uses of diodes
There are various types of diodes and these diodes are used in numerous ways.
The most basic function would be changing AC current to DC current by
removing some part of the signal. This functionality would make them rectifiers.
They are used in electrical switches and are used in surge protectors because
they can prevent a spike in the voltage.
Diodes help in performing digital logic. Millions of diodes are used similar to logic
gates and used in modern processors.
They are used for isolating signals from a supply. For example, one of the major
uses of diodes is to remove negative signals from AC current. This is known as
signal demodulation. This function is basically used in radios as a filtering system
in order to extract radio signals from a carrier wave.
They are also used in creating power supplies and voltage doublers. Using a full
wave rectifier will help to deliver a more stable voltage. Combination of a diode
with a capacitor will help to make small AC voltage multiply to create a very high
voltage.
The light emitting diodes or LEDs are used in sensors and also in laser devices
any many other light illumination devices.
Zener diodes are used as voltage regulators and varactors are used in electronic
tuning and varistors are used in suppressing AC lines
Diodes are the basis of op-amps and transistors.
