Basic electronic components
A review
Made by Yulia I. Isakova
As a template for students’
presentations
Tomsk 2015
Aim of presentation
The aim for today’s presentation is to review
basic electronic components which are used to
build semiconductor devices.
Outline
• Different types of materials
– Conductors
– Insulators
– Semiconductors
• Silicon as the most common material for semiconductors
• Basic electronic component:
– Diode
– Transistor
– Optoelectronics
• Examples of application
• Conclusion
Terminology
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Conductivity
Conductors
Insulators
Semiconductors
flow of electrons
pure silicon wafer
crystalline lattice
Device
Diodes
P-n junction
Silicon
Transistor
Lead
Optoelectronics
Liggh emmiting diode (LED)
Infrared detector
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To permit
To contain
To join together
biased
Electrical conductivity of materials
• Materials that permit flow of electrons
are called conductors (e.g., gold, silver,
copper, etc.).
• Materials that block flow of electrons
are called insulators (e.g., rubber, glass,
Teflon, mica, etc.).
• Materials whose conductivity falls
between those of conductors and
insulators are called semiconductors.
• Semiconductors are “part-time”
conductors whose conductivity can be
controlled.
Fig. 1 - Electrical conductivity
Silicon
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Atoms in a pure silicon wafer contains four electrons in outer orbit (called valence
electrons).
In the crystalline lattice structure of Si, the valence electrons of every Si atom are locked
up in covalent bonds with the valence electrons of four neighboring Si atoms.
– In pure form, Si wafer does not contain any free charge carriers.
– An applied voltage across pure Si wafer does not yield electron flow through the
wafer. – A pure Si wafer is said to act as an insulator.
In order to make useful semiconductor devices, materials such as phosphorus (P) and
boron (B) are added to Si to change Si’s conductivity.
Fig. 2 – Atomic configuration and structure of Si
Basic electronic components
1. Diodes
• A diode is a 2 lead semiconductor that acts as
a one way gate to electron flow. – Diode
allows current to pass in only one direction.
•A pn-junction diode is formed by joining
together n-type and p-type silicon.
Fig.3 – Schematic symbols of a diode
Diode: How it Works —I
When a diode is connected to
a battery as shown, electrons
from the n-side and holes
from the p-side are forced
toward the center by the
electrical field supplied by the
battery. The electrons and
holes combine causing the
current to pass through the
diode. When a diode is
arranged in this way, it is said
to be forward biased.
Fig. 5 – Schematic illustration of
a p-n junction
Basic electronic components
2. Transistor
• A three lead semiconductor device that acts as: – an electrically
controlled switch, or – a current amplifier.
• Transistor is analogous to a faucet.
– Turning faucet’s control knob alters the flow rate of water coming
out from the faucet.
– A small voltage/current applied at
transistor’s control lead controls a
larger current flow through its other
two leads.
Fig. 6 – Explanation of a transistor operation
Transistor Types: BJT, JFET, and
MOSFET
• Bipolar Junction Transistor (BJT) – NPN and PNP
• Junction Field Effect Transistor (JFET) – N-channel and Pchannel
• Metal Oxide Semiconductor FET (MOSFET) – Depletion type
(n- and p-channel) and enhancement type (n- and p-channel)
Fig. 7 - Different types of transistors
Optoelectronics Light emitting diodes
Infrared detector
In optoelectronics we deal with 2 types of electronic devices.
• Light emitting electronic devices: ones that generate electromagnetic
energy under the action of electrical field. Example: light emitting
diodes (visible and infrared light).
• Light detecting devices: ones that transform electromagnetic energy
input into electrical current/voltage. Examples: photoresistors,
photodiodes, phototransistors, etc.
Fig. 8 - Examples of optoelectronics devices: LEDs and IR detector
How LED Works
• The light-emitting section of an LED is made by joining n-type and p-type
semiconductors together to form a pn junction.
• When a voltage is applied to the P-N junction, electrons in the n side are excited and
move across the pn junction into the p side, where they combine with holes.
• As the electrons combine with the holes, photons are emitted.
• The pn-junction section of an LED is encased in an epoxy shell that is doped with light
scattering particles to diffuse light and make the LED appear brighter.
• Often a reflector placed beneath the semiconductor is used to direct the light upward.
Fig.9 – Schematic illustration of LED
Fig.10 – Principle of light generation in p-n junction
Application of LEDs
• LED uses fall into four major categories:
• Visual signals where light goes more or less directly from the source to the
human eye, to convey a message or meaning.
• Illumination where light is reflected from objects to give visual response of
these objects.
• Measuring and interacting with processes involving no human vision.[141]
• Narrow band light sensors where LEDs operate in a reverse-bias mode and
respond to incident light, instead of emitting light
Traffic light using LED
LED daytime running
lights ofAudi A4
Fig.11 – Examples of LEDs application
LED digital display that
can display four digits
and points
Conclusion
• Depending on electrical conductivity all
materials can be divided into three main
groups: conductors; insulators and
semiconductors
• Silicon is the most common material used to
build semiconductor devices.
• We have reviewed three main components
that are used to build electronic devices,
namely: diodes, transistors, LEDs.