BEE introduction slides

BASIC ELECTRONICS
ENGINEERING
18ES0402
II YEAR – I SEM
MECHANICAL
BLESSINA PREETHI R .M.E.,MISTE.
Assistant Professor

UNIT – 1: SEMICONDUCTOR DEVICES AND
APPLICATIONS
CONTENT:
1. Introduction to P-N Junction Diode and V-I
Characteristics
2. Half wave and Full wave rectifiers
3. Capacitor filters
4. Zener diode and its Characteristics
5. Zener Diode as Voltage regulator

APPLICATIONS
CONTENT:
 Introduction to BJT, its input-output and transfer characteristics,
BJT as a single stage CE amplifier, frequency response and
bandwidth, FET- input-output and transfer characteristics
 Operational amplifier and its applications: Introduction to
operational amplifiers, Op-amp input modes and parameters,
Op-amp in open loop configuration, op-amp with negative
feedback, study of practical op-amp IC 741, inverting and non-
inverting amplifier applications: summing and difference
amplifier, unity gain buffer, comparator, integrator and
differentiator.

UNIT – 3: TIMING CIRCUITS AND OSCILLATORS
CONTENT:
1. RC-timing circuits
2. IC 555 and its applications as astable and mono-
stable multi-vibrators
3. Positive feedback
4. Barkhausen's criteria for oscillation
5. R-C phase shift and Wein bridge oscillator.

UNIT – 4: DIGITAL ELECTRONICS FUNDAMENTALS
CONTENT:
1. Difference between analog and digital signals,
2. Boolean algebra,
3. Basic and Universal Gates,
4. Logic simplification using Kmap,
5. Logic ICs, half and full adder/subtractor, multiplexers,
de-multiplexers,
6. Flip-flops, shift registers, counters.
7. Block diagram of Microprocessor/Microcontroller and
their applications.

UNIT – 5: ELECTRONIC COMMUNICATION SYSTEMS
CONTENT:
1. The elements of communication system
2. IEEE frequency spectrum
3. Transmission media: wired and wireless, need of
modulation, AM and FM modulation schemes
4. Mobile communication systems: cellular concept
and block diagram of GSM system.

TEXT BOOKS:
1. Salivahanan, N.Suressh Kumar, A. Vallavaraj,
“Electronic Devices and Circuits”, Tata McGraw
Hill, Second Edition.
2. D. Roy Chowdhury, “Linear Integrated Circuits”,
New Age International (p) Ltd,2nd Edition, 2003.
3. M.Morris Mano & Michel D. Ciletti,“Digital
Design”, 5th Edition Pearson.
4. Simon Haykin, “Communication Systems”, Wiley-
India edition, 3rd edition, 2010.

APPLICATIONS
 Introduction :
 What is an atom?
 Atoms are the basic units of matter and the defining
structure of elements.

Fundamental
Particles
Nature of Charge Mass in kg
Neutron No charge 1.675 x 10-27
Proton Positive 1.675 x 10-27
Electron Negative 9.107 x 10-31
Nucleus
•Structure of an Atom:
The electrons are arranged in different orbit (2n2)

APPLICATIONS
 The outermost shell is called Valance Shell and the electrons in
this shell are called Valance Electrons.
 Each shell has energy level.
 The shell closer to the nucleus bounded tightly with low energy
level.

STRUCTURE OF METERIALS
 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.

SEMICONDUCTORS
 Semiconductors are neither conductors nor insulators.
 The forbidden gap is 1eV
 Silicon and Germanium
 The atomic number of silicon is 14 and Germanium 32

SEMICONDUCTORS : WHY SILICON?
 Valance Shell in 3
 Valance electrons are closer to
nucleus
 Valance electrons are tightly
packed
 Valance Shell in 4
 Valance electrons are farer to
nucleus
 Valance electrons are loosely
packed
 Electrons escape from atom
SILICON GERMANIUM

INTRINSIC SEMICONDUCTOR
 An intrinsic semiconductor,
also called an undoped
semiconductor or i-type
semiconductor, is a pure
semiconductor without any
significant dopant species
present. The number of
charge carriers is therefore
determined by the properties
of the material itself instead
of the amount of impurities.

 Covalent bonding in silicon:
 The outermost shell of atom is capable
to hold up to eight electrons. The atom
which has eight electrons in the
outermost orbit is said to be completely
filled and most stable. But the
outermost orbit of silicon has only four
electrons. Silicon atom needs four
more electrons to become most stable.
Silicon atom forms four covalent bonds
with the four neighboring atoms. In
covalent bonding each valence
electron is shared by two atoms.

 Electron and hole current:
 Current that is caused by electron motion is called electron
current and current that is caused by hole motion is called hole
current

EXTRINSIC SEMICONDUCTOR
 The semiconductor in which impurities are added is
called extrinsic semiconductor. When the impurities are
added to the intrinsic semiconductor, it becomes an
extrinsic semiconductor.
 The process of adding impurities to the semiconductor is
called doping.
 Doping increases the electrical conductivity of
semiconductor.

 Extrinsic semiconductor has high electrical
conductivity than intrinsic semiconductor.
 Hence the extrinsic semiconductors are used for the
manufacturing of electronic devices such as diodes,
transistors etc.
 The number of free electrons and holes in extrinsic
semiconductor are not equal.

 Types of impurities
 Two types of impurities are added to the semiconductor. They are
Pentavalent And Trivalent impurities.
 Trivalent impurities (P – type Semiconductor)
 Trivalent impurity atoms have 3 valence electrons. The various examples of
trivalent impurities include Boron (B), Gallium (G), Indium(In), Aluminium(Al).

 Pentavalent impurities (N – type Semiconductor)
 Pentavalent impurity atoms have 5 valence electrons. The various examples
of pentavalent impurity atoms include Phosphorus (P), Arsenic (As), Antimony
(Sb), etc.
Free
electron Covalent
Bond
Pentavalent
impurity

1.1. INTRODUCTION OF PN JUNCTION:
 The Extrinsic semiconductor has two types
 In N – type, the electrons are majority carriers and holes are minority
carriers
 In P – type, the Holes are majority carriers and electrons are minority
carriers
 These two types are chemically combined with special fabrication
technique to form PN Junction.
 Such combination forms a popular device called Diode.
1.1. PN Junction Diode
P - TYPE N - TYPE

P - TYPE N - TYPE

 Diffusion Current:
 The processes that follow after the formation of a p-n junction are of
two types – diffusion and drift. As we know, there is a difference in
the concentration of holes and electrons at the two sides of a
junction, the holes from the p-side diffuse to the n-side and the
electrons from the n-side diffuse to the p-side. These give rise to a
diffusion current across the junction.

1.1. 2. EXPLANATION OF PN JUNCTION DIODE:
 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.
 The p-side is called anode(A) and the n-side is called cathode(K).

1.1. 2. BIASING OF PN JUNCTION DIODE:
 There are three biasing conditions for p-n junction diode and this is based on the
voltage applied:
 Zero bias: There is no external voltage applied to the p-
n junction diode.
 Forward bias: The positive terminal of the voltage
potential is connected to the p-type while the negative
terminal is connected to the n-type.
 Reverse bias: The negative terminal of the voltage
potential is connected to the p-type and the positive is
connected to the n-type.

1.1. 3. WORKING OF PN JUNCTION DIODE:
 Working of Diode in Forward bias :
 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.

1.1. 3. WORKING OF PN JUNCTION DIODE:
 Reverse bias:
 When a diode is connected to a battery as shown, holes in the n-side are forced to the
left while electrons in the p-side are forced to the right. This results in an empty zone
round the pn- junction that is free of charge carries creating a depletion region. This
depletion region acts as an insulator preventing current from flowing through the
diode. When a diode is arranged in this way, it is said to be reverse biased.

1
 1. In a PN junction with no external voltage, the electric field between
acceptor and donor ions is called a

A.Peak
 B.Barrier
 C.Threshold
 D.Path
1.1. PN Junction Diode Questions

 2. In a PN junction the potential barrier is due to the charges on
either side of the junction, these charges are

A.Majority carriers
 B.Minority carriers
 C.Both (a) and (b)
 D.Fixed donor and acceptor ions

 3. The capacitance of a reverse biased PN junction

A.Increases as reverse bias is increased
 B.Decreases as reverse bias is increased
 C.Increases as reverse bias is decreased
 D.Is insignificantly low

 4. In an unbiased PN junction

A.The junction current is due to minority carriers only
 B.The junction current at equilibrium is zero as equal but opposite
carriers are crossin
 C.The junction current reduces with rise in temperature
 D.The junction current at equilibrium is zero as charges do not
cross the junction
 g the junction

 5. For a PN junction diode, the current in reverse bias may be

A.Few miliamperes
 B.Between 0.2 A and 15 A
 C.Few amperes
 D.Few micro or nano amperes

 6. When PN junction is in forward bias, by increasing the battery
voltage

A.Circuit resistance increases
 B.Current through P-N junction increases
 C.Current through P-N junction decreases
 D.None of the above happens


 7. When a PN junction is reverse-biased
A.Holes and electrons tend to concentrate towards the junction
 B.The barrier tends to break down
 C.Holes and electrons tend to move away from the junction
 D.None of the above


 8. In a PN junction when the applied voltage overcomes the ........
potential, the diode current is large, which is known as .............
A. Depletion, negative bias
 B. Reverse, reverse bias
 C. Resistance, reverse bias
 D. Barrier, forward bias


 9. A PN junction is said to be forward biased when

A.Positive terminal of the battery is connected to P-side and the
negative side to the N-side
 B.Junction is earthed
 C.N-side is connected directly to the p-side
 D.Positive terminal of the battery is connected to N-side and the
negative side to the P-side


 10. A PN junction

A. Has low resistance in forward as well as reverse directions
 B. Has high resistance in forward as well as reverse directions
 C. Conducts in forward direction only
 D. Conducts in reverse direction only


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