Electro – Intro to Electro

What is Electronics?

 is the study of how to control the flow of electrons.

 It deals with circuits made up of components that control the flow of electricity, such as
vacuum tubes, transistors, diodes, integrated circuits, optoelectronics, and sensors,
associated passive electrical components, and interconnection technologies.
Electronic Components

 An electronic component is any physical entity in an electronic system used to affect

the electrons or their associated fields.
 Components are generally intended to be connected together, usually by being soldered
to a printed circuit board (PCB), to create an electronic circuit with a particular function
(for example an amplifier, radio receiver, or oscillator).
 Components may be packaged singly, or in more complex groups as integrated circuits.
Some common electronic components
are capacitors, inductors, resistors, diodes, transistors, etc.
 Components are often categorized as active (e.g. transistors and thyristors)
or passive (e.g. resistors, diodes, inductors and capacitors).
One of the earliest Electronic Component

 Vacuum Tubes (Thermionic valves)

 were among the earliest electronic components.
 were almost solely responsible for the electronics revolution of the first half of the twentieth
century.
 allowed for vastly more complicated systems and gave us radio, television, phonographs, radar,
long-distance telephony and much more.
 played a leading role in the field of microwave and high power transmission as well as television
receivers until the middle of the 1980s.
 Since that time, solid-state (semiconductor devices) devices have all but completely taken over.
Vacuum tubes are still used in some specialist applications such as high power RF
amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave
devices.
Electricity
Atom

 Atom is a Greek word which means “indivisible.”

 The Greeks believed that matter can be broken down into very small invisible particles
called atoms.
 Greek philosophers such as Democritus and John Dalton put forward the concept of the
atom.
Structure of an atom can be basically divided into two parts:

 An atomic nucleus
 Extra nucleus part
Note:

 Conductors electrons are ranging from 1 to 3 electrons.

 Semiconductors has exactly 4 electrons.
 Insulators electrons are ranging from 5-6 electrons.
Electricity

 There are two types of electrical signals , the Alternating Current (AC) and the Direct
Current (DC).
 Alternating Current – electricity flows in alternating direction. This kind of current is
measured in Hertz (hz) .
 Direct Current – electricity flows in one direction.

 A circuit is a complete and closed path through which electric current can flow. In other
words, a closed circuit would allow the flow of electricity between power and ground. An
open circuit would break the flow of electricity between power and ground.
Basic Components
Resistor

 As the name implies, resistors add resistance to the circuit and reduces the flow of electrical current. It is
represented in a circuit diagram as a pointy squiggle with a value next to it.
 The different markings on the resistor represent different values of resistance. These values are measured
in ohms.
 You read the values from left to right towards the (typically) gold band. The first two colors represent the
resistor value, the third represents the multiplier, and the fourth (the gold band) represents the tolerance or
precision of the component. You can tell the value of each color by looking at a resistor color value chart.
 Or... to make your life easier, you could simply look up the values using a graphical resistance calculator.
Capacitors

 A capacitor is a component that stores electricity and then discharges it into the circuit when there is a drop
in electricity. You can think of it as a water storage tank that releases water when there is a drought to
ensure a steady stream.
 Capacitors are measured in Farads. The values that you will typically encounter in most capacitors are
measured in picofarad (pF), nanofarad (nF), and microfarad (uF). These are often used interchangeably and
it helps to have a conversion chart at hand.
 The most commonly encountered types of capacitors are ceramic disc capacitors that look like tiny M&Ms
with two wires sticking out of them and electrolytic capacitors that look more like small cylindrical tubes
with two wires coming out the bottom (or sometimes each end).
Cont.

 Ceramic disc capacitors are non-polarized, meaning that electricity can pass through them no
matter how they are inserted in the circuit.
 Electrolytic capacitors are typically polarized. This means that one leg needs to be connected to
the ground side of the circuit and the other leg must be connected to power. If it is connected
backwards, it won't work correctly. Electrolytic capacitors have the value written on them,
typically represented in uF. They also mark the leg which connects to ground with a minus
symbol (-).
Diodes

 Diodes are components which are polarized. They only allow electrical current to pass through them in one
direction. This is useful in that it can be placed in a circuit to prevent electricity from flowing in the wrong
direction.
 Another thing to keep in mind is that it requires energy to pass through a diode and this results in a drop of
voltage. This is typically a loss of about 0.7V.
 The ring found on one end of the diode indicates the side of the diode which connects to ground. This is the
cathode. It then follows that the other side connects to power. This side is the anode.
Transistors

 A transistor takes in a small electrical current at its base pin and amplifies it such that a much larger current
can pass between its collector and emitter pins. The amount of current that passes between these two pins
is proportional to the voltage being applied at the base pin.
 There are two basic types of transistors, which are NPN and PNP. These transistors have opposite polarity
between collector and emitter. For a very comprehensive intro to transistors check out this page.
 NPN transistors allow electricity to pass from the collector pin to the emitter pin. They are represented in a
schematic with a line for a base, a diagonal line connecting to the base, and a diagonal arrow pointing away
from the base.
 PNP transistors allow electricity to pass from the emitter pin to the collector pin. They are represented in a
schematic with a line for a base, a diagonal line connecting to the base, and a diagonal arrow pointing
towards the base.
Integrated Circuits

 An integrated circuit is an entire specialized circuit that has been miniaturized and fit onto one small chip with each
leg of the chip connecting to a point within the circuit. These miniaturized circuits typically consist of components
such as transistors, resistors, and diodes.
 For instance, the internal schematic for a 555 timer chip has over 40 components in it.
 The round notch on one edge of the IC chip indicates the top of the chip. The pin to the top left of the chip is
considered pin 1. From pin 1, you read sequentially down the side until you reach the bottom (i.e. pin 1, pin 2, pin
3..). Once at the bottom, you move across to the opposite side of the chip and then start reading the numbers up
until you reach the top again.
 Keep in mind that some smaller chips have a small dot next to pin 1 instead of a notch at the top of the chip.
Potentiometers

 Potentiometers are variable resistors. In plain English, they have some sort of knob or slider that you turn or
push to change resistance in a circuit. If you have ever used a volume knob on a stereo or a sliding light dimmer,
then you have used a potentiometer.
 Potentiometers are measured in ohms like resistors, but rather than having color bands, they have their value
rating written directly on them (i.e. "1M"). They are also marked with an "A" or a "B, " which indicated the type
of response curve it has.
 Potentiometers marked with a "B" have a linear response curve. This means that as you turn the knob, the
resistance increases evenly (10, 20, 30, 40, 50, etc.). The potentiometers marked with an "A" have a logarithmic
response curve. This means that as you turn the knob, the numbers increase logarithmically (1, 10, 100, 10,000
etc.)
LEDs

 LED stands for light emitting diode. It is basically a special type of diode that lights up when electricity passes
through it. Like all diodes, the LED is polarized and electricity is only intended to pass through in one direction.
 There are typically two indicators to let you know what direction electricity will pass through and LED. The first
indicator that the LED will have a longer positive lead (anode) and a shorter ground lead (cathode). The other
indicator is a flat spot on the side of the LED to indicate the negative (cathode) lead. Keep in mind that not all
LEDs have this indication notch (or that it is sometimes wrong).
 Like all diodes, LEDs create a voltage drop in the circuit, but typically do not add much resistance. In order to
prevent the circuit from shorting, you need to add a resistor in series.
 You may be tempted to wire LEDs in series, but keep in mind that each consecutive LED will result in a voltage
drop until finally there is not enough power left to keep them lit. As such, it is ideal to light up multiple LEDs by
wiring them in parallel. However, you need to make certain that all of the LEDs have the same power rating
before you do this (different colors often are rated differently).
Switches

 A switch is basically a mechanical device that creates a break in a circuit. When you activate the switch, it
opens or closes the circuit. This is dependent on the type of switch it is.
 Normally open (N.O.) switches close the circuit when activated.
 Normally closed (N.C.) switches open the circuit when activated.
 As switches get more complex they can both open one connection and close another when activated. This
type of switch is a single-pole double-throw switch (SPDT).
 If you were to combine two SPDT switches into one single switch, it would be called a double-pole double-
throw switch (DPDT). This would break two separate circuits and open two other circuits, every time the
switch was activated.
Batteries

 A battery is a container which converts chemical energy into electricity. To over-simplify the matter, you can
say that it "stores power."
 By placing batteries in series you are adding the voltage of each consecutive battery, but the current stays
the same. For instance, a AA-battery is 1.5V. If you put 3 in series, it would add up to 4.5V. If you were to
add a fourth in series, it would then become 6V.
 By placing batteries in parallel the voltage remains the same, but the amount of current available doubles.
This is done much less frequently than placing batteries in series, and is usually only necessary when the
circuit requires more current than a single series of batteries can offer.
Breadboards

 Breadboards are special boards for prototyping electronics. They are covered with a grid of holes, which are
split into electrically continuous rows.
 In the central part there are two columns of rows that are side-by-side. This is designed to allow you to be
able to insert an integrated circuit into the center. After it is inserted, each pin of the integrated circuit will
have a row of electrically continuous holes connected to it.
 In this way, you can quickly build a circuit without having to do any soldering or twisting wires together.
Simply connect the parts that are wired together into one of the electrically continuous rows.
 On each edge of the breadboard, there typically runs two continuous bus lines. One is intended as a power
bus and the other is intended as a ground bus. By plugging power and ground respectively into each of
these, you can easily access them from anywhere on the breadboard.
Wire

 In order to connect things together using a breadboard, you either need to use a component or a wire.
 Wires are nice because they allow you to connect things without adding virtually no resistance to the
circuit. This allows you to be flexible as to where you place parts because you can connect them together
later with wire. It also allows you to connect a part to multiple other parts.
 It is recommended that you use insulated 22awg (22 gauge) solid core wire for breadboards. Red wire
typically indicates a power connection and black wire represents a ground connection.
Semiconductors
What is a semiconductor?

 Semiconductors are used extensively in electronic circuits. As its name implies, a semiconductor is a
material that conducts current, but only partly.
 Most semiconductors are crystals made of certain materials, most commonly silicon.
 Silicon is used extensively as a semiconductor in solid state devices in the computer and
microelectronics devices.
 Other usage of silicons:
 Dynamo
 Transformer plates

 SILICONES
 SILICONE OIL
 COSMETICS
 HAIR CONDITIONERS
 SEALANT
 etc
Other examples of semiconductors

 Other examples of semiconductors are

germanium, gallium arsenide, and
elements near the so-called "metalloid
staircase" on the periodic table.
 After silicon, gallium arsenide is the
second most
common semiconductor and is used in
laser diodes, solar cells, microwave-
frequency integrated circuits
and others.
How are elements made?

 The electrons in an atom are organized in layers, these layers are called shells, the
outermost shell is called the valence shell, the electrons in this shell are the ones that form
bonds with neighboring atoms, such bonds are called covalent bonds.
 Semiconductors, on the other hand, typically have four electrons in their valence shell.
 If all the neighboring atoms are of the same type, it’s possible for all the valence electrons
to bind with valence electrons from other atoms. When that happens, the atoms arrange
themselves into structures called crystals usually silicon crystals.

Conductors electrons are ranging from 1 to 3 electrons.

Semiconductors has exactly 4 electrons.
Insulators electrons are ranging from 5-6 electrons.
Thus, each silicon atom is bonded with four other silicon atoms.
2 Types of Semiconductor

 N-type: An N-type semiconductor material has an excess of electrons. ...

 P-type: In a P-type semiconductor material there is a shortage of electrons, i.e. there are
'holes' in the crystal lattice.
2 Types of Extrinsic Semiconductor

 N-type material is created by introducing impurity elements that have five valence
electrons (pentavalent), such as Antimony(Sb), Arsenic(As) and Phosphorus(P).
 P-type material is formed by doping a pure germanium or silicon crystal with impurity
atoms having three valence electrons. The elements most frequently used for this purpose
are Boron(B), Gallium(Ga) and Indium(In).
Majority and minority carriers

 In an n-type material, the electron is called the majority carrier and the hole will be the
minority carrier.
 In a p-type material, the hole is the majority carrier and the electron is the minority carrier.
DIODE
Diodes

 Electronic devices created by bringing together a p-type and an n-type region within the
same semiconductor lattice.
Semiconductor diode

 Semiconductor diode is formed by simply bringing these materials together (constructed

from the same base – Ge or Si).
 At the instant the two materials are joined, the electrons and holes in the region of the
junction will combine.

Depletion Region - this region of

uncovered positive and negative ions
is called the depletion region due to
the depletion of carriers in this region.
Three possibilities for a diode

 1. No bias, (𝑉𝐷 = 0 V)
 No Applied Voltage or No Bias
conditions Is the effect without
any external voltage being
applied to the actual PN
junction resulting in the junction
being in a state of equilibrium.
Cont.

 2. Forward bias, (𝑉𝐷 > 0 V)

 It is established by applying the
positive potential to the p-type
material and the negative
potential to the n-type material.
 The application of a forward-
bias potential 𝑉𝐷 will “pressure”
electrons in the n-type material
and holes in the p-type material
to recombine with the ions near
the boundary and reduce the
width of the depletion region.
 Cont.

 3. Reverse bias, (𝑉𝐷 < 0 V)

 REVERSE-BIAS CONDTION. If an external
potential of V volts is applied across the
p-n junction such that the positive
terminal is connected to the n-type
material and the negative terminal is
connected to the p-type material. The
number of uncovered positive ions in the
depletion region of the n-type material
will increase due to the larger number of
“free” electrons drawn to the positive
potential of the applied voltage.
 The net effect, therefore, will widen the
depletion region.
Comparisons about Diodes
Why use forward biased and reverse biased?

Forward biased Reverse biased

 A forward-biased diode conducts current  A reversed-biased diode prohibits current.
and drops a small voltage across it.  It prevents current from going through it.
 In actuality, a very small amount of
current can and does go through a
reverse-biased diode, called the leakage
current, but it can be ignored for most
purposes.
Cont.
Short Quiz

 1. What happens to the thickness of the depletion region in a PN junction when an

external voltage is applied to a forward bias diode?
 2. When “P” and “N” type semiconductor pieces are brought into close contact, free
electrons from the “N” piece will rush over to fill holes in the “P” piece, creating a zone on
both sides of the contact region devoid of charge carriers. What is this zone called, and
what are its electrical characteristics?
 3. Is this diode forward-biased or reverse biased?
 4. Insert a diode into this circuit schematic in the correct
direction to make it forward-biased by the battery voltage:
Conclusion

 Semiconductors are materials whose electrical properties lie between Conductors and
Insulators. Ex : Silicon and Germanium
 P-type: A P-type material is one in which holes are majority carriers i.e. they are
positively charged materials (++++)
 N-type: A N-type material is one in which electrons are majority charge carriers i.e. they
are negatively charged materials (-----)
 Diodes are electronic devices created by bringing together a p-type and n-type region
within the same semiconductor lattice. Used for rectifiers, LED etc
Cont.

 Forward Bias: Connect positive of the Diode to positive of supply…negative of Diode to

negative of supply
 Reverse Bias: Connect positive of the Diode to negative of supply…negative of diode to
positive of supply.
Cont.

 Characteristics of Diode
 Diode always conducts in one direction.
 Diodes always conduct current when “Forward Biased” ( Zero resistance)
 Diodes do not conduct when Reverse Biased (Infinite resistance)
 Voltage across a forward and reverse biased
 It can be demonstrated through the use of solid-state physics that the general characteristics of a
semiconductor diode can be defined by the ff equation for the forward- and reverse-bias regions.
End of Presentation