Lecture notes of basic electronics
CHAPTER – 1[CO1]
Active Components
An active component is a device that has an analog electronic filter with the ability to amplify a signal or
produce a power gain. There are two types of active components: electron tubes and semiconductors or
solid-state devices. A typical active component would be an oscillator, transistor or integrated circuit. An
active component works as an alternating-current circuit in a device, which works to increase the active
power, voltage or current. An active component is able to do this because it is powered by a source of
electricity that is separate from the electrical signal.
Voltage Sources
A voltage source is an example of an active component in a circuit. When current leaves from the
positive terminal of the voltage source, energy is being supplied to the circuit. As per the definition of an
active element, a battery can also be considered as an active element, as it continuously delivers energy
to the circuit during discharging.
Current Sources
A current source is also considered an active component. The current supplied to the circuit by an ideal
current source is independent of circuit voltage. As a current source is controlling the flow of charge in a
circuit, it is classified as an active element.
Voltage Sources
A voltage source is an example of an active component in a circuit. When current leaves from the
positive terminal of the voltage source, energy is being supplied to the circuit. As per the definition of an
active element, a battery can also be considered as an active element, as it continuously delivers energy to
the circuit during discharging.
Current Sources
A current source is also considered an active component. The current supplied to the circuit by an ideal
current source is independent of circuit voltage. As a current source is controlling the flow of charge in a
circuit, it is classified as an active element.
Passive Components
A passive component is an electronic component which can only receive energy, which it can either
dissipate, absorb or store it in an electric field or a magnetic field. Passive elements do not need any
form of electrical power to operate.As the name ‘passive’ suggests – passive devices do not provide gain
or amplification. Passive components cannot amplify, oscillate, or generate an electrical signal.
Common examples of passive components include:
Resistors
Inductors
Capacitors
Transformers
Resistors
A resistor is taken as a passive element since it can not deliver any energy to a circuit. Instead resistors
can only recieve energy which they can dissipate as heat as long as current flows through it.
Inductors
An inductor is also considered as passive element of circuit, because it can store energy in it as a
magnetic field, and can deliver that energy to the circuit, but not in continuous basis. The energy
absorbing and delivering capacity of an inductor is limited and transient in nature. That is why an
inductor is taken as a passive element of a circuit.
Capacitors
A capacitor is considered as a passive element because it can store energy in it as electric field. The
energy dealing capacity of a capacitor is limited and transient – it is not actually supplying energy, it is
storing it for later use.As such it is not considered an active component since no energy is being supplied
or amplified.
Transformers
A transformer is also a passive electronic component. Although this can seem surprising since
transformers are often used to raise voltage levels – remember that power is kept constant.When
transformers step up (or step down) voltage, power and energy remain the same on the primary and
secondary side. As energy is not actually being amplified – a transformer is classified as a passive
element.
Phase
In electronic signalling, phase is a definition of the position of a point in time (instant) on
a waveform cycle.
Wavelength
Wavelength is defined as the distance from a particular height on the wave to the next
spot on the wave where it is at the same height and going in the same direction.
The following formula can be used to determine wavelength:
λ=v/ƒ
spectrum
A spectrum (plural spectra or spectrums)[1] is a condition that is not limited to a specific set of
values but can vary, without steps, across a continuum
Cycle
One complete set of positive and negative values of a signal is known as cycle. A cycle
o
is normally specified in terms of angular measure spread over 360 or 2π
Frequency
Frequency is a measurement of how many cycles can happen in a certain amount
of time… cycle per second.
Frequency is the number of waves per unit time. Period is the reciprocal of that - the
duration of a single wave.
If a motor is running so that it completes 50 revolutions in one second, I would say that
it has a frequency of 50 Hertz.
Hertz is the unit of frequency, and just means how many cycles per second.
o It is abbreviated as Hz.
o It is named after Heinrich Hertz, one member of the Hertz family that made
many important contributions to physics.
In formulas frequency appears as an "f".
Since frequency and period are exact inverses of each other, there is a very basic pair
of formulas you can use to calculate one if you know the other…
measured in meters, just like any length.
Usually
it
is
Any of the parts of the wave that are pointing up like mountains are called crests. Any
part that is sloping down like a valley is a trough.
Amplitude
Amplitude is the magnitude of the wave - how high it goes on the y axis. Wavelength
is basically the same thing as period - the length of a single wave on the x axis..
Draw Saw tooth wave ,sine wave, square wave, triangular wave
CHAPTER – 2[CO2,CO3]
PN Junction Diode
A PN-junction diode is formed when a p-type semiconductor is fused to an n-type semiconductor
creating a potential barrier voltage across the diode junction. The effect of adding this additional energy
source results in the free electrons being able to cross the depletion region from one side to the other.
The behaviour of the PN junction with regards to the potential barrier’s width produces an asymmetrical
conducting two terminal device, better known as the PN Junction Diode
.
A PN Junction Diode is one of the simplest semiconductor devices around, and which has the
characteristic of passing current in only one direction only. However, unlike a resistor, a diode does not
behave linearly with respect to the applied voltage as the diode has an exponential current-voltage ( I-V
) relationship and therefore we can not described its operation by simply using an equation such as
Ohm’s law.
The V-I characteristics or voltage-current characteristics of the p-n junction diode is shown in the below
figure. The horizontal line in the below figure represents the amount of voltage applied across the p-n
junction diode whereas the vertical line represents the amount of current flows in the p-n junction diode.
IF = Forward Biased Current of diode
VF = Forward Biased Voltage of diode
Io = Reverse biased Saturation Current of Diode
IR = Reverse biased Current of Diode
Forward Biase V-I characteristic of P-N diode.
 When anode is positive with respect to cathode , diode is said to be forward biased.
 with increase of the source voltage Vs from zero value , initially diode current is zero. from Vs=0
to cut-in voltage , the forward current is very small .
 cut-in voltage is also known as threshold voltage or turn-on voltage. beyond cut-in voltage ,the
diode current rises rapidly and diode said to conduct.
 for silicon diode, the cut-in voltage is around 0.7. when diode conducts, there is a forward voltage
drop of the order of 0.8 to 1V
Reverse Biase V-I characteristic of P-N diode.
 When cathode is positive with respect to anode the , the diode said to be reverse biased.
 In the reverse biased condition. a small reverse current leakage current , of the order of
microampers or milliampers flow .
 the leakage current is almost independent of the reverse voltage until this voltage reach
breakdown voltage at this reverse breakdown, voltage remains almost constant but reverse current
becomes quite high limited only by the external circuit resistance .
 A large reverse break down voltage associated with high reverse current, leads to excessive
power loss that may be destroy the diode.
Bridge Rectifier
A bridge rectifier is a type of full wave rectifier which uses four or more diodes in a bridge circuit
configuration to efficiently convert the Alternating Current (AC) into Direct Current (DC).
Bridge Rectifier Construction
The construction diagram of a bridge rectifier is shown in the below figure. The bridge rectifier is made
up of four diodes namely D1, D2, D3, D4 and load resistor RL. The four diodes are connected in a closed
loop (Bridge) configuration to efficiently convert the Alternating Current (AC) into Direct Current (DC).
The main advantage of this bridge circuit configuration is that we do not require an expensive center
tapped transformer, thereby reducing its cost and size.The construction diagram of a bridge rectifier is
shown in the below figure. The bridge rectifier is made up of four diodes namely D1, D2, D3, D4 and load
resistor RL.
The input AC signal is applied across two terminals A and B and the output DC signal is obtained across
the load resistor RL which is connected between the terminals C and D.
The four diodes D1, D2, D3, D4 are arranged in series with only two diodes allowing electric current
during each half cycle. For example, diodes D1 and D3 are considered as one pair which allows electric
current during the positive half cycle whereas diodes D2 and D4 are considered as another pair which
allows electric current during the negative half cycle of the input AC signal.
Half wave rectifier
A half wave rectifier is a type of rectifier which converts the positive half cycle (positive current) of the
input signal into pulsating DC (Direct Current) output signal.
or
A half wave rectifier is a type of rectifier which allows only half cycle (either positive half cycle or
negative half cycle) of the input AC signal while the another half cycle is blocked.
A half wave rectifier is a type of rectifier which converts the positive half cycle (positive current) of the
input signal into pulsating DC (Direct current) output signal.
For example, if the positive half cycle is allowed then the negative half cycle is blocked. Similarly, if the
negative half cycle is allowed then the positive half cycle is blocked. However, a half wave rectifier will
not allow both positive and negative half cycles at the same time.Therefore, the half cycle (either
positive or negative) of the input signal is wasted.
The half wave rectifier is the simplest form of the rectifier. We use only a single diode to construct the
half wave rectifier.
The half wave rectifier is made up of an AC source, transformer (step-down), diode, and resistor (load).
The diode is placed between the transformer and resistor (load).
Full wave rectifier
A full wave rectifier is a type of rectifier which converts both half cycles of the AC signal into pulsating
DC signal. A full-wave rectifier is a type of rectifier which converts both half cycles of the AC signal into
pulsating DC signal. As shown in the above figure, the full wave rectifier converts both positive and
negative half cycles of the input AC signal into output pulsating DC signal.
The full wave rectifier is further classified into two types: center tapped full wave rectifier and full wave
bridge rectifier.In this tutorial, center tapped full wave rectifier is explained.Before going to the working
of a center tapped full wave rectifier, let’s first take a look at the center tapped transformer. Because
the center tapped transformer plays a key role in the center tapped full wave rectifier.
Intrinsic Semiconductor




An intrinsic semiconductor is formed from a highly pure semiconductor material thus also known
as pure semiconductors. These are basically undoped semiconductors that do not have doped
impurity in it.
At room temperature, intrinsic semiconductors exhibit almost negligible conductivity. As no any
other type of element is present in its crystalline structure.
The group IV elements of the periodic table form an intrinsic semiconductor. However,
mainly silicon and germanium are widely used. This is so because in their case only small energy
is needed in order to break the covalent bond.
The figure below shows the crystalline structure of silicon:

The figure above clearly shows that silicon consists of 4 electrons in the valence shell. Here, 4
covalent bonds are formed between the electrons of the silicon atom.

When the temperature of the crystal is increased then the electrons in the covalent bond gain
kinetic energy and after breaking the covalent bond it gets free. Thus, the movement of free
electrons generates current.
The rise in temperature somewhat increases the number for free electrons for conduction.

Extrinsic Semiconductor







Extrinsic Semiconductors are those that are the result of adding an impurity to a pure
semiconductor. These are basically termed as an impure form of semiconductors.
The process by which certain amount of impurity is provided to a pure semiconductor is known
as doping. So, we can say a pure semiconductor is doped to generate an extrinsic semiconductor.
These are highly conductive in nature. However, unlike intrinsic semiconductor, extrinsic
semiconductors are of two types p-type and an n-type semiconductor.
It is noteworthy here that the classification of the extrinsic semiconductor depends on the type of
element doped to the pure semiconductor.
The p-type semiconductors are formed by introducing group III elements or trivalent impurity
into the pure semiconductor. These are also known as an acceptor impurity, as a trivalent
impurity has only 3 electrons in the valence shell.
The n-type semiconductors are formed by the addition of group V elements or pentavalent
impurity to a pure semiconductor. These are termed as donor impurity, as a pentavalent impurity
holds 5 electrons in its valence shell.
The figure below represents the crystalline structure of n-type semiconductor:


Here, the above figure clearly shows that a pentavalent impurity is doped to a pure silicon crystal.
In this case, 4 electrons of phosphorus are covalently bonded with the adjacent silicon atom. But,
still, a free electron is left in this case.
Thus, the movement of these free electrons generates high conduction. Also, when the
temperature is increased then it causes the covalent bond to get a breakdown. Hence generating
more free electrons.
P-type semiconductor
A p-type semiconductor is a type of semiconductor.When the trivalent impurity is added to an intrinsic
or pure semiconductor (silicon or germanium), then it is said to be an p-type semiconductor. Trivalent
impurities such as Boron (B), Gallium (Ga), Indium(In), Aluminium(Al) etc are called acceptor impurity.
Ordinary semiconductors are made of materials that do not conduct (or carry) an electric current very well
but are not highly resistant to doing so. They fall half way between conductors and insulators. An electric
current occurs when electrons move through a material. In order to move, there must be an electron 'hole'
in the material for the electron to move into. A p-type semiconductor has more holes than electrons. This
allows the current to flow along the material from hole to hole but only in one direction.
Semiconductors are most often made from silicon. Silicon is an element with four electrons in its outer
shell. To make a p-type semiconductor extra materials like boron or aluminium are added to the silicon.
These materials have only three electrons in their outer shell. When the extra material replaces some of
the silicon it leaves a 'hole' where the fourth electron would have been if the semiconductor was pure
silicon.
N-type semiconductor
When pentavalent impurity is added to an intrinsic or pure semiconductor (silicon or germanium), then it
is said to be an n-type semiconductor. Pentavalent impurities such as phosphorus, arsenic, antimony etc
are called donor impurity. An N-Type semiconductor is created by adding pentavalent impurities
like phosphorus (P), arsenic (As), antimony (Sb), or bismuth (Bi). A pentavalent impurity is called a
donor atom because it is ready to give a free electron to a semiconductor. The impurities are called
dopants. The purpose of doing this is to make more charge carriers, or electron wires available in the
material for conduction. In n-type semiconductors the number of electrons is more than the holes, so
electrons are measured as majority charge carriers and holes are referred to as minority charge carriers
Pi Filter
Definition: Pi filter consists of a shunt capacitor at the input side, and it is followed by an L-section filter.
The output from the rectifier is directly given across capacitor. The pulsating DC output voltage is
filtered first by the capacitor connected at the input side and then by choke coil and then by another
shunt capacitor. The construction arrangement of all the components resembles the shape of Greek
letter Pi (π). Thus it is called Pi filter. Besides, the capacitor is present at the input side. Thus, it is also
called capacitor input filter.
Significance of Capacitor input filter or Pi filter (π- filter)
The ultimate aim of a filter is to achieve ripple free DC voltage. The filters we have discussed in our
previous articles are also efficient in removing AC ripples from the output voltage of rectifier, but Pi filter
is more efficient in removing ripples as it consists of one more capacitor at the input side.
Working of Pi filter (π- filter)
The output voltage coming from rectifier also consist of AC components. Thus it is a crucial need to
remove these AC ripples to improve the performance of the device. The output from the rectifier is
directly applied to the input capacitor. The capacitor provides a low impedance to AC ripples present in
the output voltage and high resistance to DC voltage. Therefore, most of the AC ripples get bypassed
through the capacitor in input stage only.
The residual AC components which are still present in filtered DC signal gets filtered when they pass
through the inductor coil and through the capacitor connected parallel across the load. In this way, the
efficiency of filtering increases multiple times.
In the case of L-section filter, one inductor and capacitor were present so if some AC ripples say 1% is
left after filtering that can be removed in Pi-filter. Thus, Pi filter is considered more efficient.
T Filter
T filter uses two shunt inductors and a coupling capacitor. These single-stage filters can act as
low pass, high pass, band pass, and band stop.
Figure. T filter



The components can be chosen symmetric or not, depending on the required frequency
characteristics.
The high-pass T filter in the illustration, has a very low impedance at high frequencies, and a very
high impedance at low frequencies.
That means that it can be inserted in a transmission line, resulting in the high frequencies being
passed and low frequencies being reflected.
CHAPTER – 3[CO4]
PNP Transistor
Definition: The transistor in which one n-type material is doped with two p-type materials such type of
transistor is known as PNP transistor. It is a current controlled device. The small amount of base current
controlled both the emitter and collector current. The PNP transistor has two crystal diodes connected
back to back. The left side of the diode in known as the emitter-base diode and the right side of the
diode is known as the collector-base diode.
The hole is the majority carriers of the PNP transistors which constitute the current in it. The current
inside the transistor is constituted because of the changing position of holes and in the leads of the
transistor it is because of the flow of the electrons. The PNP transistor turns on when a small current
flows through the base. The direction of current in PNP transistor is from the emitter to collector.
The letter of the PNP transistor indicates the voltage requires by the emitter, collector and the base of
the transistor. The base of the PNP transistor has always been negative with respect to the emitter and
collector. In PNP transistor, the electrons are taken from the base terminal. The current which enters
into the base is amplified into the collector ends.
Symbol of PNP Transistor
The symbol of PNP transistor is shown in the figure below. The inward arrow shows that the direction of
current in PNP transistor is from the emitter to collector.
Construction of PNP Transistor
The construction of PNP transistor is shown in the figure below. The emitter-base junction is connected
in forward biased, and the collector-base junction is connected in reverse biased. The emitter which is
connected in the forward biased attracts the electrons towards the battery and hence constitutes the
current to flow from emitter to collector.
Block-diagram-pnp-transistor
The base of the transistor is always kept positive with respect to the collector so that the hole from the
collector junction cannot enter into the base. And the base-emitter is kept in forward due to which the
holes from the emitter region enter into the base and then into the collector region by crossing the
depletion region.
Working of PNP Transistor
The emitter-base junction is connected in forward biased due to which the emitter pushes the holes in
the base region. These holes constitute the emitter current. When these electrons move into the N-type
semiconductor material or base, they combined with the electrons. The base of the transistor is thin and
very lightly doped. Hence only a few holes combined with the electrons and the remaining are moved
towards the collector space charge layer. Hence develops the base current.
working-pnp-transistor
The collector base region is connected in reverse biased. The holes which collect around the depletion
region when coming under the impact of negative polarity collected or attracted by the collector. This
develops the collector current. The complete emitter current flows through the collector current IC.
NPN Transistor
Definition: The transistor in which one p-type material is placed between two n-type materials is known
as NPN transistor. The NPN transistor amplifies the weak signal enter into the base and produces strong
amplify signals at the collector end. In NPN transistor, the direction of movement of an electron is from
the emitter to collector region due to which the current constitutes in the transistor. Such type of
transistor is mostly used in the circuit because their majority charge carriers are electrons which have
high mobility as compared to holes.
Construction of NPN Transistor
The NPN transistor has two diodes connected back to back. The diode on the left side is called an
emitter-base diode, and the diodes on the left side are called collector-base diode. These names are
given as per the name of the terminals.
npn-transistor
The NPN transistor has three terminals, namely emitter, collector and base. The middle section of the
NPN transistor is lightly doped, and it is the most important factor of the working of the transistor. The
emitter is moderately doped, and the collector is heavily doped.
Circuit Diagram of NPN Transistor
The circuit diagram of the NPN transistor is shown in the figure below. The collector and the base circuit
is connected in reverse biased while the emitter and base circuit is connected in forward biased. The
collector is always connected to the positive supply, and the base is in negative supply for controlling the
ON/OFF states of the transistor.
Working of NPN Transistor
The circuit diagram of the NPN transistor is shown in the figure below. The forward biased is applied
across the emitter-base junction, and the reversed biased is applied across the collector-base junction.
The forward biased voltage VEB is small as compared to the reverse bias voltage VCB.
The emitter of the NPN transistor is heavily doped. When the forward bias is applied across the emitter,
the majority charge carriers move towards the base. This causes the emitter current IE. The electrons
enter into the P-type material and combine with the holes.
The base of the NPN transistor is lightly doped. Due to which only a few electrons are combined and
remaining constitutes the base current IB. This base current enters into the collector region. The
reversed bias potential of the collector region applies the high attractive force on the electrons reaching
collector junction. Thus attract or collect the electrons at the collector.
The whole of the emitter current is entered into the base. Thus, we can say that the emitter current is
the sum of the collector or the base current.
Transistor as a Switch



A transistor works in active region when worked as an Amplifier. When a transistor
works as a Switch it works in Cutoff and Saturation Regions.
In the Cutoff State both Emitter Base Junction and Collector Base junctions are reverse
biased. But in saturation region both junctions are forward biased. Switch is a very useful
and important application of transistors.
In most digital IC’s transistors will work as a switch to make power consumption very
low. It is also a very useful circuit for an electronics hobbyist as it can be used as a driver,
inverter etc..

Circuit Diagram – Transistor as a Switch
Transistor as a Switch Circuit Diagram




From the above circuit we can see that the control input Vin is given to base through a
current limiting resistor Rb and Rc is the collector resistor which limits the current
through the transistor.
In most cases output is taken from collector but in some cases load is connected in the
place of Rc.
ON = Saturation
OFF = Cutoff
Transistor as a Switch – ON
Transistor as a Switch ON

Transistor will become ON ( saturation ) when a sufficient voltage V is given to input.

During this condition the Collector Emitter voltage Vce will be approximately equal to
zero, ie the transistor acts as a short circuit.

For a silicon transistor it is equal to 0.3v. Thus collector current Ic = Vcc/Rc will flows.
Transistor as a Switch – OFF
Transistor as a Switch OFF
Transistor will be in OFF ( cutoff ) when the input Vin equal to zero. During this state transistor
acts as an open circuit and thus the entire voltage Vcc will be available at collector.
Difference between BJT and FET








Bipolar junction transistors are bipolar devices, in this transistor there is a flow of both
majority & minority charge carriers.
Field effect transistors are unipolar devices, in this transistor there are only the majority
charge carriers flows.
Bipolar junction transistors are current controlled.
Field effect transistors are voltage controlled.
In many applications FETs are used than bipolar junction transistors.
Bipolar junction transistor consist of three terminals namely emitter, base and collector.
These terminals are denoted by E, B and C.
Field effect transistor consist of three terminals namely source, drain and gate. These
terminals are denoted by S, D and G.
The input impedance of field effect transistors has high compared with bipolar junction
transistors.








A BJT needs a small amount of current to switch on the transistor.The heat dissipated on
bipolar stops the total number of transistors that can be fabricated on the chip.
Whenever the ‘G’ terminal of the FET transistor has been charged, no more current is
required to keep the transistor ON.
The BJT is responsible for overheating due to a negative temperature co-efficient.
FET has a +Ve temperature coefficient for stopping over heating.
BJTs are applicable for low current applications.
FETS are applicable for low voltage applications.
FETs have low to medium gain.
BJTs have a higher max frequency and a higher cutoff frequency.
CHAPTER – 4[CO4]
What is an Oscillator?
An oscillator is a circuit which produces a continuous, repeated, alternating waveform without any
input. Oscillators basically convert unidirectional current flow from a DC source into an alternating
waveform which is of the desired frequency, as decided by its circuit components.
Hartley Oscillator
Hartley Oscillator is a type of harmonic oscillator which was invented by Ralph Hartley in 1915. These
are the Tuned Circuit Oscillators which are used to produce the waves in the range of radio frequency
and hence are also referred to as RF Oscillators. Its frequency of oscillation is decided by its tank circuit
which has a capacitor connected in parallel with the two serially connected inductors, as shown by
Figure 1.
Here the RC is the collector resistor while the emitter resistor RE forms the stabilizing network. Further
the resistors R1 and R2 form the voltage divider bias network for the transistor in common-emitter CE
configuration. Next, the capacitors Ci and Co are the input and output decoupling capacitors while the
emitter capacitor CE is the bypass capacitor used to bypass the amplified AC signals. All these
components are identical to those present in the case of a common-emitter amplifier which is biased
using a voltage divider network. However, Figure 1 also shows one more set of components viz., the
inductors L1 and L2 and the capacitor C which form the tank circuit (shown in red enclosure).
On switching ON the power supply, the transistor starts to conduct, leading to an increase in the
collector current, IC which charges the capacitor C. On acquiring the maximum charge feasible, C starts
to discharge via the inductors L1 and L2. This charging and discharging cycles result in the damped
oscillations in the tank circuit. The oscillation current in the tank circuit produces an AC voltage across
the inductors L1 and L2 which are out of phase by 180o as their point of contact is grounded.
At this state, if one makes the gain of the circuit to be slightly greater than the feedback ratio given by
(if the coils are wound on the same core with M indicating the mutual inductance)
Colpitts Oscillator
Colpitts Oscillator is a type of LC oscillator which falls under the category of Harmonic Oscillator and was
invented by Edwin Colpitts in 1918. Figure 1 shows a typical Colpitts oscillator with a tank circuit in
which an inductor L is connected in parallel to the serial combination of capacitors C1 and C2 (shown by
the red enclosure).
Other components in the circuit are the same as that found in the case of common-emitter CE which is
biased using a voltage divider network i.e. RC is the collector resistor, RE is the emitter resistor which is
used to stabilize the circuit and the resistors R1 and R2 form the voltage divider bias network. Further,
the capacitors Ci and Co are the input and output decoupling capacitors while the emitter capacitor CE is
the bypass capacitor used to bypass the amplified AC signals.
Here, as the power supply is switched ON, the transistor starts to conduct, increasing the collector
current IC due to which the capacitors C1 and C2 get charged. On acquiring the maximum charge
feasible, they start to discharge via the inductor L. During this process, the electrostatic energy stored in
the capacitor gets converted into magnetic flux which in turn is stored within the inductor in the form of
electromagnetic energy. Next, the inductor starts to discharge which charges the capacitors once again.
Likewise, the cycle continues which gives rise to the oscillations in the tank circuit.
Further the figure shows that the output of the amplifier appears across C1 and thus is in-phase with the
tank circuit’s voltage and makes-up for the energy lost by re-supplying it. On the other hand, the voltage
feedback to the transistor is the one obtained across the capacitor C2, which means the feedback signal
is out-of-phase with the voltage at the transistor by 180o. This is due to the fact that the voltages
developed across the capacitors C1 and C2 are opposite in polarity as the point where they join is
grounded. Further, this signal is provided with an additional phase-shift of 180o by the transistor which
results in a net phase-shift of 360o around the loop, satisfying the phase-shift criterion of Barkhausen
principle.
At this state, the circuit can effectively act as an oscillator producing sustained oscillations by carefully
monitoring the feedback ratio given by (C1 / C2). The frequency of such a Colpitts Oscillator depends on
the components in its tank circuit and is given by
Where, the Ceff is the effective capacitance of the capacitors expressed as
CHAPTER – 5[CO5]
Cables
A cable may refer to any of the following:
1. Alternatively referred to as a cord, connector or plug, a cable is one or more wires covered in a plastic
covering that allows for the transmission of power or data between devices. The picture is an example
of what the power cord may look like for your computer or monitor. The power cord is one example of
thousands of other cables found in and around computers.
Types Of Cables :-
Coaxial cable
Coaxial cable is a type of copper cable specially built with a metal shield and other components
engineered to block signal interference. It is primarily used by cable TV companies to connect their
satellite antenna facilities to customer homes and businesses. It is also sometimes used by telephone
companies to connect central offices to telephone poles near customers. Some homes and offices use
coaxial cable, too, but its widespread use as an Ethernet connectivity medium in enterprises and data
centers has been supplanted by the deployment of twisted pair cabling.
How coaxial cables work
Coax cables have concentric layers of electrical conductors and insulating material. This construction
ensures signals are enclosed within the cable and prevents electrical noise from interfering with the
signal.
The center conductor layer is a thin conducting wire, either solid or braided copper. A dielectric layer,
made up of an insulating material with very well-defined electrical characteristics, surrounds the wire. A
shield layer then surrounds the dielectric layer with metal foil or braided copper mesh. The whole
assembly is wrapped in an insulating jacket. The outer metal shield layer of the coax cable is typically
grounded in the connectors at both ends to shield the signals and as a place for stray interference
signals to dissipate.
A key to coaxial cable design is tight control of cable dimensions and materials. Together, they ensure
the characteristic impedance of the cable takes on a fixed value. High-frequency signals are partially
reflected at impedance mismatches, causing errors.
Optical Fiber Cable
An optical fiber cable is a type of cable that has a number of optical fibers bundled together, which are
normally covered in their individual protective plastic covers. Optical cables are used to transfer digital
data signals in the form of light up to distances of hundreds of miles with higher throughput rates than
those achievable via electrical communication cables. All optical fibers use a core of hair-like transparent
silicon covered with less refractive indexed cladding to avoid light leakage to the surroundings. Due to
the extreme sensitivity of the optical fiber, it is normally covered with a high-strength, lightweight
protective material like Kevlar. Optical fiber cable is widely used in fiber optic communications.
Two common types of fiber optics are:
Single-mode fiber (SMF)
Multi-mode fiber (MMF)
Interconnection between multiple fiber strands is much more complex and difficult to achieve, than the
ones between electrical cables.
Working of Optical Fiber Cable :
Light travels down a fiber-optic cable by bouncing repeatedly off the walls. Each tiny photon (particle of
light) bounces down the pipe like a bobsleigh going down an ice run. Now you might expect a beam of
light, traveling in a clear glass pipe, simply to leak out of the edges. But if light hits glass at a really
shallow angle (less than 42 degrees), it reflects back in again—as though the glass were really a mirror.
This phenomenon is called total internal reflection. It's one of the things that keeps light inside the pipe.
The other thing that keeps light in the pipe is the structure of the cable, which is made up of two
separate parts. The main part of the cable—in the middle—is called the core and that's the bit the light
travels through. Wrapped around the outside of the core is another layer of glass called the cladding.
The cladding's job is to keep the light signals inside the core. It can do this because it is made of a
different type of glass to the core. (More technically, the cladding has a lower refractive index.)
Twisted-pair cable
A twisted-pair cable is a cable made by intertwining two separate insulated wires. There are two twisted
pair types: shielded and unshielded. A STP (Shielded Twisted Pair) cable has a fine wire mesh
surrounding the wires to protect the transmission and a UTP (Unshielded Twisted Pair) cable does not.
Shielded cable is used in older telephone networks, as well as network and data communications to
reduce outside interference.
Types Of Twisted pair Cable :
Unshielded Twisted Pair Cable
Unshielded twisted pair (UTP) cables are found in many Ethernet networks and telephone systems. For
indoor telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair
color code originally developed by AT&T Corporation. A typical subset of these colors (white/blue,
blue/white, white/orange, orange/white) shows up in most UTP cables. The cables are typically made
with copper wires measured at 22 or 24 American Wire Gauge (AWG),[4] with the colored insulation
typically made from an insulator such as polyethylene or FEP and the total package covered in a
polyethylene jacket.
Shielded Twisted Pair Cable
Shielded twisted pair (STP) cable was originally designed by IBM for token ring networks that include
two individual wires covered with a foil shielding, which prevents electromagnetic interference, thereby
transporting data faster.
STP is similar to unshielded twisted pair (UTP); however, it contains an extra foil wrapping or copper
braid jacket to help shield the cable signals from interference. STP cables are costlier when compared to
UTP, but has the advantage of being capable of supporting higher transmission rates across longer
distances.