minor project

1. 1
Chapter-1
INTRODUCTION
The scope of the study is to analyse and study the I-V characteristics curves of PN junction diode, Zener
diode and LED. Through this project we will know and learn about different aspects and principles
involved in construction, working and behaviour of different elements. We will try to study the input and
output behaviour of these elements and how input fluctuations affect the output.
Figure 1.1 PN junction Apparatus

2. 2
Chapter-2
PN JUNCTION DIODE
2.1 INTRODUCTION
Donor impurities (pentavalent) are introduced into one-side and acceptor impurities into the
other side of a single crystal of an intrinsic semiconductor to form a p-n diode with a junction
called depletion region (this region is depleted off the charge carriers). This region gives rise
to a potential barrier Vγ called Cut- in Voltage. This is the voltage across the diode at which it
starts conducting. The P-N junction can conduct beyond this Potential. The P-N junction
supports uni-directional current flow. If +ve terminal of the input supply is connected to anode
(P-side) and –ve terminal of the input supply is connected to cathode (N- side), then diode is
said to be forward biased. In this condition the height of the potential barrier at the junction is
lowered by an amount equal to given forward biasing voltage. Both the holes from p-side and
electrons from n-side cross the junction simultaneously and constitute a forward current
(injected minority current – due to holes crossing the junction and entering N-side 13of the
diode, due to electrons crossing the junction and entering P-side of the diode). Assuming
current flowing through the diode to be very large, the diode can be approximated as short-
circuited switch. If –ve terminal of the input supply is connected to anode (p-side) and +ve
terminal of the input supply is connected to cathode (n-side) then the diode is said to be reverse
biased. In this condition an amount equal to reverse biasing voltage increases the height of the
potential barrier at the junction. Both the holes on p-side and electrons on n-side tend to move
away from the junction thereby increasing the depleted region. However, the process cannot
continue indefinitely, thus a small current called reverse saturation current continues to flow in
the diode. This small current is due to thermally generated carriers. Assuming current flowing
through the diode to be negligible, the diode can be approximated as an open circuited switch.
The volt-ampere characteristics of a diode explained by following equation:
I = Io(Exp(V/ ηVT)-1)
I=current flowing in the diode
Io=reverse saturation current

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V=voltage applied to the diode
VT=volt-equivalent of temperature=kT/q=T/11,600=26mV(@ room temp).
η=1 (for Ge) and 2 (for Si)
It is observed that Ge diode has smaller cut-in-voltage when compared to Si diode. The reverse
saturation current in Ge diode is larger in magnitude when compared to silicon diode.
2.2 EQUILIBRIUM
In a p–n junction, without an external applied voltage, an equilibrium condition is reached in
which a potential difference is formed across the junction. This potential difference is called
build in potential.
After joining p-type and n-type semiconductors, electrons from the n region near the p–n
interface tend to diffuse into the p region leaving behind positively charged ions in the n region
and being recombined with holes, forming negatively charged ions in the p region. Likewise,
holes from the p-type region near the p–n interface begin to diffuse into the n-type region,
leaving behind negatively charged ions in the p region and recombining with electrons, forming
positive ions in the n region. The regions near the p–n interface lose their neutrality and most
of their mobile carriers, forming the space charge region or depletion layer (see figure A).
Figure 2.1 A p–n junction in thermal equilibrium with zero-bias voltage applied.

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Electron and hole concentration are reported with blue and red lines, respectively. Grey regions
are charge-neutral. Light-red zone is positively charged. Light-blue zone is negatively charged.
The electric field is shown on the bottom, the electrostatic force on electrons and holes and the
direction in which the diffusion tends to move electrons and holes. (The log concentration
curves should actually be smoother with slope varying with field strength.)
The electric field created by the space charge region opposes the diffusion process for both
electrons and holes. There are two concurrent phenomena: the diffusion process that tends to
generate more space charge, and the electric field generated by the space charge that tends to
counteract the diffusion. The carrier concentration profile at equilibrium is shown in figure
A with blue and red lines. Also shown are the two counterbalancing phenomena that establish
equilibrium.
Figure 2.2. A p–n junction in thermal equilibrium with zero-bias voltage applied.

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Under the junction, plots for the charge density, the electric field, and the voltage are reported.
The space charge region is a zone with a net charge provided by the fixed ions
(donors or acceptors) that have been left uncovered by majority carrier diffusion. When
equilibrium is reached, the charge density is approximated by the displayed step function. In
fact, since the y-axis of figure A is log-scale, the region is almost completely depleted of
majority carriers (leaving a charge density equal to the net doping level), and the edge between
the space charge region and the neutral region is quite sharp (see figure B, Q(x) graph). The
space charge region has the same magnitude of charge on both sides of the p–n interfaces, thus
it extends farther on the less doped side in this example (the n side in figures A and B).
2.3 FORWARD BIAS
In forward bias, the p-type is connected with the positive terminal and the n-type is connected
with the negative terminal.
PN junction operation in forward-bias mode, showing reducing depletion width. The panels
show energy band diagram, electric field, and net charge density. Both p and n junctions are
doped at a 1e15/cm3 (0.00016C/cm3) doping level, leading to built-in potential of ~0.59 V.
Reducing depletion width can be inferred from the shrinking charge profile, as fewer dopants
are exposed with increasing forward bias. Observe the different quasi-fermi levels for
conduction band and valence band in n and p regions (red curves)
With a battery connected this way, the holes in the p-type region and the electrons in the n-type
region are pushed toward the junction and start to neutralize the depletion zone, reducing its
width. The positive potential applied to the p-type material repels the holes, while the negative
potential applied to the n-type material repels the electrons. The change in potential between
the p side and the n side decreases or switches sign. With increasing forward-bias voltage, the
depletion zone eventually becomes thin enough that the zone's electric field cannot counteract
charge carrier motion across the p–n junction, which as a consequence reduces electrical
resistance. The electrons that cross the p–n junction into the p-type material (or holes that cross
into the n-type material) will diffuse into the nearby neutral region. The amount of minority
diffusion in the near-neutral zones determines the amount of current that may flow through the
diode.

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Only majority carriers (electrons in n-type material or holes in p-type) can flow through a
semiconductor for a macroscopic length. With this in mind, consider the flow of electrons
across the junction. The forward bias causes a force on the electrons pushing them from the N
side toward the P side. With forward bias, the depletion region is narrow enough that electrons
can cross the junction and inject into the p-type material. However, they do not continue to
flow through the p-type material indefinitely, because it is energetically favourable for them to
recombine with holes. The average length an electron travels through the p-type material before
recombining is called the diffusion length, and it is typically on the order of micrometres.[2]
Although the electrons penetrate only a short distance into the p-type material, the electric
current continues uninterrupted, because holes (the majority carriers) begin to flow in the
opposite direction. The total current (the sum of the electron and hole currents) is constant in
space, because any variation would cause charge build-up over time (this is Kirchhoff's current
law). The flow of holes from the p-type region into the n-type region is exactly analogous to
the flow of electrons from N to P (electrons and holes swap roles and the signs of all currents
and voltages are reversed).
Therefore, the macroscopic picture of the current flow through the diode involves electrons
flowing through the n-type region toward the junction, holes flowing through the p-type region
in the opposite direction toward the junction, and the two species of carriers constantly
recombining in the vicinity of the junction. The electrons and holes travel in opposite
directions, but they also have opposite charges, so the overall current is in the same direction
on both sides of the diode, as required.
The Shockley diode equation models the forward-bias operational characteristics of a p–n
junction outside the avalanche (reverse-biased conducting) region.

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2.4 REVERSE BIAS
Figure2.3 A silicon p–n junction in reverse bias.
Connecting the p-type region to the negative terminal of the battery and the n-type region to
the positive terminal corresponds to reverse bias. If a diode is reverse-biased, the voltage at
the cathode is comparatively higher than at the anode. Therefore, very little current will flow
until the diode breaks down. The connections are illustrated in the adjacent diagram.
Because the p-type material is now connected to the negative terminal of the power supply, the
'holes' in the p-type material are pulled away from the junction, leaving behind charged ions
and causing the width of the depletion region to increase. Likewise, because the n-type region
is connected to the positive terminal, the electrons will also be pulled away from the junction,
with similar effect. This increases the voltage barrier causing a high resistance to the flow of
charge carriers, thus allowing minimal electric current to cross the p–n junction. The increase
in resistance of the p–n junction results in the junction behaving as an insulator.
The strength of the depletion zone electric field increases as the reverse-bias voltage increases.
Once the electric field intensity increases beyond a critical level, the p–n junction depletion
zone breaks down and current begins to flow, usually by either the Zener or the avalanche
breakdown processes. Both of these breakdown processes are non-destructive and are
reversible, as long as the amount of current flowing does not reach levels that cause the
semiconductor material to overheat and cause thermal damage.
This effect is used to advantage in Zener diode regulator circuits. Zener diodes have a low
breakdown voltage. A standard value for breakdown voltage is for instance 5.6 V. This means
that the voltage at the cathode cannot be more than about 5.6 V higher than the voltage at the
anode (although there is a slight rise with current), because the diode will break down – and

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therefore conduct – if the voltage gets any higher. This in effect limits the voltage over the
diode.
Another application of reverse biasing is Varicap diodes, where the width of the depletion
zone (controlled with the reverse bias voltage) changes the capacitance of the diode
2.5 CURRENT ACROSS DEPLETION REGION
The Shockley ideal diode equation characterizes the current across a p–n junction as a function
of external voltage and ambient conditions (temperature, choice of semiconductor, etc.). To
see how it can be derived, we must examine the various reasons for current. The convention is
that the forward (+) direction be pointed against the diode's built-in potential gradient at
equilibrium.
 Forward Current
 Diffusion Current
 Reverse Current
 Field Current
 Generation Current
2.6 CIRCUIT DIAGRAM
2.6.1 FORWARD BIAS
Figure 2.4 Circuit diagram of forward bias.

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2.6.2 REVERSE BIAS
Figure 2.5 Circuit diagram of reverse bias
2.7 PRECAUTIONS
1. While doing the experiment do not exceed the ratings of the diode. This may lead to damage
of the diode.
2. Connect voltmeter and Ammeter in correct polarities as shown in the circuit diagram.
3. Do not switch ON the power supply unless you have checked the circuit connections as per
the circuit diagram.
2.8 EXPERIMENT
2.8.1 FORWARD BIASED CONDITION
1. Connect the PN Junction diode in forward bias i.e. Anode is connected to positive of the
power supply and cathode is connected to negative of the power supply.
2. Use a Regulated power supply of range (0-30) V and a series resistance of 1kΏ.
3. For various values of forward voltage (Vf) note down the corresponding values of forward
current(If).

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2.8.2 REVERSE BIASED CONDITION
1. Connect the PN Junction diode in Reverse bias i.e; anode is connected to negative of the
power supply and cathode is connected to positive of the power supply.
2. For various values of reverse voltage (Vr) note down the corresponding values of reverse
current (Ir).
2.9 GRAPH
1. Take a graph sheet and divide it into 4 equal parts. Mark origin at the centre of the graph
sheet.
2. Now mark +ve x-axis as Vf
-ve x-axis as Vr
+ve y-axis as If
-ve y-axis as Ir.
3. Mark the readings tabulated for diode forward biased condition in first Quadrant and diode
reverse biased condition in third Quadrant.
` Figure 2.6 Graph of forward & reverse biased condition

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2.10 CALCULATION FROM GRAPH
Static forward Resistance Rdc = Vf/If Ω
Dynamic forward Resistance rac = ΔVf/ΔIf Ω
Static Reverse Resistance Rdc =Vr/Ir Ω
Dynamic Reverse Resistance rac = ΔVr/ΔIr Ω
2.11 APPLICATION OF PN JUNCTION DIODE
1.PN junction in reverse biased configuration is sensitive (generates an electron-hole pair) to
light from 400-1000nm which includes VISIBLE Light (400nm to 700nm). So all/most of the
sensors involving capturing light information will use a photodiode. PN junction in reverse
biased configuration is the most widely used sensor compared to any other sensor. For example,
all the digital cameras use an array of photodiodes to capture light and produce an image &
Solar Cells
2. PN junction (which has direct energy bandgap) in forward biased condition produces light
when biased with a current. All LED lighting uses a PN junction diode. Voltage across PN
junction biased at a constant current has a negative temperature coefficient. Difference between
the PN junction voltages of two differently biased diodes has a positive temperature coefficient.
These properties are used to create Temperature Sensors, Reference voltages (Bandgap).
Various circuits like Rectifiers, Reactors for Voltage Controlled Oscillators (VCO) etc.

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Chapter-3
ZENER DIODE
The diode is one of the basic components in electronic circuits. When you want to know about
voltage considerations you should know about the diodes. The diode is basically made up
of semiconductors which have two characteristics, ‘P’ type and ‘N’ type. The ‘P’type and ‘N’
type semiconductors represent positive and negative type semiconductors.‘P’type
semiconductor will have excess amount of holes in configuration and ‘N’ type semiconductor
will have excess amount of electrons. If both types of characteristics present in a single crystal,
then it can be termed as a diode. The positive terminal of the battery connects with the ‘P’ side
and the negative side is connected with the ‘N’ side. Let’s discuss about Zener diode working,
it is nothing but a simple diode connecting in reverse bias.
Figure 3.1 Symbol of Zener diode
It is mainly a special property of the diode rather than any special type of equipment. The
person named Clearance Zener invented this property of the diode that’s why it is named after
him as a remembrance. The special property of the diode is that there will be a breakdown in
the circuit if the voltage applied across a reversely biased circuit. This does not allow the
current to flow across it. When the voltage across the diode is increased, temperature also
increases and the crystal ions vibrate with greater amplitude and all these leads to the
breakdown of the depletion layer. The layer at the junction of ‘P’ type and ‘N’ type. When the
applied voltage exceeds an specific amount Zener breakdown takes place.

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Figure 3.2 Zener diode & its characteristics
Zener diode is nothing but a single diode connected in a reverse bias mode and Zener diode
can be connected in reverse bias positive in a circuit as shown as picture. We can connect it for
different applications.
3.1 UNBIASED SEMICONDUCTOR DIODE
In normal conditions, holes from the p side tend to diffuse to a low concentration region and
the same thing happens for electrons from n-side. Thus the holes diffuse to the n-side and the
electrons diffuse to the p-side. This results in accumulation of charges around the junction,
forming a depletion region.

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Figure 3.3 Characteristics of unbiased semiconductor diode
An electric polarity or electric dipole is formed across the junction, causing flow of flux from
n side to p side. This results in varying negative electric field intensity, generating an electric
potential across the junction. This electric potential is actually the threshold voltage of the diode
and is around 0.6V for silicon and 0.2V for Germanium. This acts as a potential barrier for flow
of majority charge carriers and the device does not conduct.
Now when a normal diode is biased such that a negative voltage is applied to the n side and
positive voltage to the p side, the diode is said to be in forward biasing condition. This applied
voltage tends to decrease the potential barrier after it goes beyond the threshold voltage.

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At this point and afterwards, the majority carriers cross the potential barrier and the device
starts conducting with flow of current through it.
When the diode is biased in reverse condition to above, the applied voltage is such that it adds
to the potential barrier and hinders the flow of majority carriers. However, it does allow the
flow of minority carriers (holes in n type and electrons in p type). As this reverse bias voltage
increases, the reverse current tends to increase gradually.
At a certain point, this voltage is such that it causes breakdown of the depletion region, causing
a massive increase in the flow of current. This is where the Zener diode working comes into
play.
3.2 PRINCIPLE & WORKING OPERATION
3.2.1 ZENER BRAEKDOWN
This type of breakdown occurs for a reverse bias voltage between 2 to 8V. Even at this low
voltage, the electric field intensity is strong enough to exert a force on the valence electrons of
the atom such that they are separated from the nuclei. This results in formation of mobile
electron hole pairs, increasing the flow of current across the device. Approximate value of this
field is about 2*10^7 V/m.
This type of break down occurs normally for highly doped diode with low breakdown voltage
and larger electric field. As temperature increases, the valence electrons gain more energy to
disrupt from the covalent bond and less amount of external voltage is required. Thus Zener
breakdown voltage decreases with temperature.
As stated above the basic principle behind the working of a Zener diode lies in the cause of
breakdown for a diode in reverse biased condition. Normally there are two types of breakdown-
Zener and Avalanche.

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Figure 3.4 Working &Operation of Zener diode
3.3 EXPERIMENT
3.3.1 FORWARD BIASED CONDITION
1. Connect the Zener diode in forward bias i.e; anode is connected to positive of the power
supply and cathode is connected to negative of the power supply as in circuit

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2. Use a Regulated power supply of range (0-30) V and a series resistance of 1kΏ.
3. For various values of forward voltage (Vf) note down the corresponding values of forward
current(If).
3.3.2 CIRCUIT DIAGRAM
Forward Bias
Figure 3.5 Forward bias of Zener diode
3.3. REVERSE BIAS CONDITION
1. Connect the Zener diode in Reverse bias i.e; anode is connected to negative of the power
supply and cathode is connected to positive of the power supply as in circuit.
2. For various values of reverse voltage (Vr) note down the corresponding values of reverse
current (Ir).

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Figure 3.6 Reverse bias of Zener diode
3.4 CHARACTERISTICS MODEL
Figure 3.7 Characteristics Model

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Calculations from graph
Cut in voltage = ---------- (v)
Break down voltage = ------------(v)
3.5 APPLICATION OF ZENER DIODE
3.5.1 ZENER DIODE AS A VOLTAGE
In a DC circuit, Zener diode can be used as a voltage regulator or to provide voltage reference.
The main use of Zener diode lies in the fact that the voltage across a Zener diode remains
constant for a larger change in current. This makes it possible to use a Zener diode as a constant
voltage device or a voltage regulator.
In any power supply circuit, a regulator is used to provide a constant output (load) voltage
irrespective of variation in input voltage or variation in load current. The variation in input
voltage is called line regulation, whereas the variation in load current is called load regulation.
Figure 3.8 Zener Diode as voltage regulator
A simple circuit involving Zener diode as a regulator requires a resistor of low value connected
in series with the input voltage source. The low value is required so as to allow the maximum
flow of current through the diode, connected in parallel. However, the only constraint being,
the current through Zener diode should not be less than minimum Zener diode current. Simply

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put, for a minimum input voltage and a maximum load current, the Zener diode current should
always be Izmin.
While designing a voltage regulator using Zener diode, the latter is chosen with respect to its
maximum power rating. In other words, the maximum current through the device should be: -
Imax = Power/Zener Voltage
Since the input voltage and the required output voltage is known, it is easier to choose a Zener
diode with a voltage approximately equal to the load voltage, i.e. Vz ~=Vo.
The value of the series resistor is chosen to be
R =(Vin – Vz)/(Izmin + IL), where IL = Load Voltage/Load resistance.
Note that for load voltages up to 8V, a single Zener diode can be used. However, for load
voltages beyond 8V, requiring Zener voltages of higher voltage value, it is advisable to use a
forward biased diode in series with the Zener diode. This is because the Zener diode at higher
voltage follows the avalanche breakdown principle, having a positive temperature of
coefficient.
Hence a negative temperature coefficient diode is used for compensation. Of course, these
days, practical temperature compensated Zener diodes are used.
3.5.2. ZENER DIODE AS A REFERENCE VOLTAGE
Figure 3.9 Zener diode as voltage reference

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In power supplies and many other circuits, Zener diode finds its application as a constant
voltage provider or a voltage reference. The only conditions are that the input voltage should
be greater than Zener voltage and the series resistor should have a minimum value such that
the maximum current flows through the device.
3.5.3. ZENER DIODE AS A VOLTAGE CLAMPER
In a circuit involving AC input source, different from the normal PN diode clamping circuit, a
Zener diode can also be used. The diode can be used to limit the peak of the output voltage to
Zener voltage at one side and to about 0V at other side of the sinusoidal waveform.
Figure 3.10 Zener diode as voltage clamper
In the above circuit, during positive half cycle, once the input voltage is such that the Zener
diode is reverse biased, the output voltage is constant for a certain amount of time till the
voltage starts decreasing.
Now during the negative half cycle, the Zener diode is in forward biased connection. As the
negative voltage increases till forward threshold voltage, the diode starts conducting and the
negative side of the output voltage is limited to the threshold voltage.

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Chapter-4
LED
4.1 INTRODUCTION
Figure 4.1 Structure of LED
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps
in many devices and are increasingly used for other lighting. Introduced as a practical electronic
component in 1962, early LEDs emitted low-intensity red light, but modern versions are
available across the visible, ultraviolet and infrared wavelengths, with very high brightness.
The LED consists of a chip of semiconducting material doped with impurities to create a p-n
junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or
cathode, but not in the reverse direction. Charge-carriers—electrons and holes—flow into the
junction from electrodes with different voltages. When an electron meets a hole, it falls into a
lower energy level, and releases energy in the form of a photon.
The wavelength of the light emitted, and thus its colour depends on the band gap energy of the
materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes
recombine by a non-radiative transition which produces no optical emission, because these are

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indirect band gap materials. The materials used for the LED have a direct band gap with
energies corresponding to near-infrared, visible or near-ultraviolet light.
LED development began with infrared and red devices made with gallium arsenide. Advances
in materials science have enabled making devices with ever-shorter wavelengths, emitting light
in a variety of colours. LEDs are usually built on an n-type substrate, with an electrode attached
to the p-type layer deposited on its surface. P-type substrates, while less common, occur as
well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate.
Most materials used for LED production have very high refractive indices. This means that
much light will be reflected back into the material at the material/air surface interface. Thus,
light extraction in LEDs is an important aspect of LED production, subject to much research
and development.
4.2 WORKING PRINCIPLE
To understand the working principle of light emitting diode, we first have to understand a basic
of quantum theory. According to this theory, when an electron comes down from its higher
energy level to lower energy level, it emits energy in form of a photon. The energy of this
photon is equal to the energy gap between these two energy levels. When a pn junction diode
is forward biased, current flows through the diode. Flow of current through the semiconductor
is caused by both flow of free electrons in opposite direction of current and flow of holes in the
direction of current. Hence during flow of these charge carriers, there will be recombination’s.
Recombination mean electrons in condition band jump down to the valence band. During this
jump electron will emit electromagnetic energy in form of photons whose energy is equal to
forbidden energy gap E.g. Again according to quantum theory, energy of a photon is the
product of frequency of electromagnetic radiation and Planck constant. Where h is Planck
constant. Again velocity of electromagnetic radiation is fixed and it is equal to the speed of
light i.e. c. The frequency of radiation f is related to velocity of light as f = c / λ. Where λ is
wavelength of the electromagnetic radiation. Hence from equation (1) So we have seen that
wavelength of electromagnetic radiation is inversely proportional to the forbidden energy gap.
In normal silicon, germanium semiconductor this forbidden energy gaps between condition
and valence band are such that entire radiation of electromagnetic wave during recombination
is in the form of inferred radiation. The wavelengths of the inferred are out of our visible range
so we cannot see it. Inferred electromagnetic radiation is nothing but heat. This is because,

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silicon and germanium semiconductor are not direct gap semiconductor rather these are indirect
gap semiconductor. In indirect gap semiconductor the maximum energy level of valence band
and minimum energy level of conduction band do not occur at same momenta of electrons.
Hence during recombination’s of electrons and holes that is migration of electrons from
conduction band to valence band the momentum of electrons would be changed.
The photons originated from these electrons will be mostly utilized for the electron momentum.
In direct gap semiconductor the maximum of valence band and minimum of conduction band
occur at same electron momenta. Hence, there will be no change of momentum of electrons
during migration from conduction band to valence band so the photons originated due that
migration have not to provide momentum to electrons. As a result, the photons are emitted
from the surface of semiconductor crystal. There is some special type of specially alloyed direct
energy gap semiconductors whose energy gap between condition and valence band are such
that the electromagnetic radiation emitted during recombination’s has wavelengths within our
visible range. That means in these special semiconductors when recombination’s between
electrons and holes occur, there will be emissions of light. This is how a light emitting diode
works.
The wave length of output optical signals depends upon the band gap energy. The output wave
length can be engineered within certain limits by using compound semiconductors, so that a
particular colour can be observed, provided the output is in visible range.
Application of LED or Light Emitting Diode
Today almost everywhere LEDs lights are used and the application of LED is huge. First we
are going to see through the list, then we will categorize the application of these.
In motorcycle and bicycle lights.
In traffic lights and signals.
In message displaying boards.
In light bulbs and many more.

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Figure 4.2 Energy diagram of LED
Now, practically if we sit to list all the applications it will be a non-ending list. So, here we are
classifying the use in to some parts.
Indicators and Signs: - These are mainly used in traffic signals, exit signs, light weight message,
displaying box etc.
Lighting: - Light Emitting Diode lamps have become highly popular and as the energy
consumption is very low for them, they are also being made by LED s. In 2001, the Italian
village Tarrasa was the first place to convert all its lighting to LED. In television and
computer/laptop displaying, LEDs are used.
Non Visual Application:- Communication, sensor are the main area of non-visual application
of LEDs.
4.3 CIRCUIT DIAGRAM
Forward Bias

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Figure 4.3 Circuit diagram of forward bias
REVERSE BIAS
Figure 4.4 Circuit diagram of reverse bias
4.4 EXPERIMENTAL PROCEDURE
1. Give the connection as per the circuit diagram.
2. Vary the input voltages at the RPS and note down the corresponding current for the voltages.
3. Repeat the procedure for reverse bias condition and tabulate the corresponding voltages and currents.
4. Plot the graph between voltage and current for forward bias and reverse bias.

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4.5 CHARACTERISTICS CURVE OF LED
Figure 4.5 CharacteristicsofLED
4.6 APPLICATIONS OF LED
Today almost everywhere LEDs lights are used and the application of LED is huge. First we
are going to see through the list, then we will categorize the application of these.
In motorcycle and bicycle lights.
In traffic lights and signals.
In message displaying boards.
In light bulbs and many more.
Now, practically if we sit to list all the applications it will be a non-ending list. So, here we are
classifying the use in to some parts.
1. Indicators and Signs: - These are mainly used in traffic signals, exit signs, light weight
message, displaying box etc.
2. Lighting: - Light Emitting Diode lamps have become highly popular and as the energy
consumption is very low for them, they are also being made by LED s. In 2001, the Italian
Village Terrace was the first place to convert all its lighting to LED. In television and
computer/laptop displaying, LEDs are used.
3. Non Visual Application:- Communication, sensor are the main area of non-visual application
of LEDs.

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CONCIUSION
In the experiment, the main objective was
fulfilled i.e. obtain the IV characteristics of P-N junction diode for forward bias and reverse
bias circuit. Two graphs were made i.e. I versus for verification purpose, In the end, IV
characteristics of P-N Junction were discussed.