Module:1 Diode Circuits
Module:1 Diode Circuits
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Inspiration to electronics
Real life applications
Diode equation
Diode circuits: clippers, clampers
Rectifiers with and without filters
Regulated power supplies
Multiple diode circuits
What are Semiconductors?
• Have conductivity between conductors and
non-conductors or insulators
• Conductors - eg. Metals
• Insulators - eg. Such ceramics
• Semiconductors - gallium arsenide or pure
elements – eg. Germanium or silicon.
Energy Band Gaps in Materials
Fermi Level in Semiconductors
• The Fermi level of a solid-state body is the
thermodynamic work required to add one
electron to the body.
• It is a thermodynamic quantity usually
denoted by µ or EF
Properties of Semiconductors
• Semiconductors can conduct electricity under
preferable conditions or circumstances.
• This unique property makes it an excellent
material to conduct electricity in a controlled
manner as required.
Properties of Semiconductors
• Unlike conductors, the charge carriers in
semiconductors arise only because of external
energy (thermal agitation).
• It causes a certain number of valence
electrons to cross the energy gap and jump
into the conduction band, leaving an equal
amount of unoccupied energy states, i.e.
holes.
Properties of Semiconductors
• Resistivity: 10-5 to 106 Ωm
• Conductivity: 105 to 10-6 mho/m
• Temperature coefficient of
resistance: Negative
• Current Flow: Due to electrons and holes
Resistivity of Semiconductors Vs.
Temperature
• Resistivity of semiconductors decreases with
temperature because the number of charge
carriers increases rapidly with increase in
temperature
• i.e., The temperature is coefficient negative.
Properties of Semiconductors
• Semiconductor acts like an insulator at zero
kelvin.
• On increasing the temperature, it works as a
conductor.
• Due to their exceptional electrical properties,
semiconductors can be modified by doping to
make semiconductor devices suitable for energy
conversion, switches, and amplifiers.
• Semiconductors are smaller in size and possess
less weight.
Examples of Semiconductors
• Most commonly used semiconductors gallium arsenide, germanium and silicon
• Silicon is used in electronic circuit fabrication
and gallium arsenide is used in solar
cells, laser diodes etc.
Types of Semiconductors
Extrinsic Semiconductor
• Conductivity of semiconductors can be greatly
improved by introducing a small number of
suitable replacement atoms called IMPURITIES.
• Process of adding impurity atoms to the pure
semiconductor is called doping.
• Usually, only 1 atom in 107 is replaced by a
dopant atom
Extrinsic semiconductor is further classified into:
• N-type semiconductor
• P-type semiconductor
N-Type Semiconductor
• When a pure semiconductor (Silicon or Germanium)
is doped by pentavalent impurity (P, As, Sb, Bi) then,
four electrons out of five valence electrons bonds
with the four electrons of Ge or Si.
• The fifth electron of the dopant is set free.
• Thus the impurity atom donates a free electron for
conduction in the lattice and is called “Donar“.
• Since the number of free electron increases by the
addition of an impurity, the negative charge carriers
increase. Hence it is called n-type semiconductor.
P-Type Semiconductor
• When a pure semiconductor is doped with a
trivalent impurity (B, Al, In, Ga ) then, the three
valence electrons of the impurity bonds with three
of the four valence electrons of the semiconductor.
• This leaves an absence of electron (hole) in the
impurity.
• These impurity atoms which are ready to accept
bonded electrons are called “Acceptors“.
• With the increase in the number of impurities,
holes (the positive charge carriers) are increased.
Hence, it is called p-type semiconductor.
Difference between Intrinsic and
Extrinsic Semiconductors
Intrinsic Semiconductor
Extrinsic Semiconductor
Pure semiconductor
Impure semiconductor
Density of electrons is equal to
the density of holes
Density of electrons is not
equal to the density of holes
Electrical conductivity is low
Electrical conductivity is high
Dependence on temperature
only
Dependence on temperature as
well as on the amount of
impurity
No impurities
Trivalent impurity, pentavalent
impurity
Applications of Semiconductors
• Semiconductors are used in almost all electronic
devices.
• Their reliability, compactness, low cost and
controlled conduction of electricity make them
ideal to be used for various purposes in a wide
range of components and devices.
• Transistors,
diodes,
photo
sensors,
microcontrollers, integrated chips and much more
are made up of semiconductors.
Uses of Semiconductors in Everyday
life
• Temperature sensors are made with
semiconductor devices.
• They are used in 3D printing machines
• Used in microchips and self-driving cars
• Used in calculators, solar plates, computers
and other electronic devices.
• Transistor and MOSFET used as a switch in
Electrical Circuits are manufactured using the
semiconductors.
Importance of Semiconductors
• They are highly portable due to the smaller
size
• They require less input power
• Semiconductor devices are shockproof
• They have a longer lifespan
• They are noise-free while operating
PN Junction and Semiconductor
Diode
• The term PN junction is used while discussing
the term diode.
• But they’re essentially the same thing: a basic
semiconductor diode is a pn junction with
conductive terminals attached.
PN Junction Diode
PN Junction Diode
The unfilled circles on the left are holes, and the solid
circles on the right are electrons.
PN Junction Diode
• depletion region consists of holes that have
recombined with free electrons from the n-type
semiconductor and electrons that have
recombined with holes from the p-type
semiconductor
• This recombination causes the p-type portion of
the depletion region to be negatively charged
and the n-type portion of the depletion region to
be positively charged.
PN Junction Diode
• The separation of charge at the junction
results in a potential difference called
the contact potential.
• In a silicon pn-junction diode, the contact
potential is about 0.6 V.
PN Junction Diode
• Current flow through the junction due to
diffusion—
• i.e., Due to the difference in charge-carrier
concentration across the junction
• Some holes from the p-type material will
diffuse into the n-type material, and some
electrons from the n-type material will diffuse
into the p-type material.
PN Junction Diode
• However, very little current flows due to
diffusion as the contact potential acts as a
barrier to this diffusion current.
• Contact potential is termed as barrier voltage
Biasing the PN Junction Diode
• Forward Bias – Positive terminal of the supply is
connected to P-type material and negative
terminal of the supply is connected to N-type
• Forward Bias decreases the depletion layer
width.
• Reverse Bias – Negative terminal of the supply is
connected to P-type material and positive
terminal of the supply is connected to N-type
• Reverse Bias decreases the depletion layer width.
Forward Biased PN Junction
Biasing the PN Junction Diode
Ideal Diode Vs Practical Diode
Forward Biased PN Junction
Reverse Biased PN Junction
VI Characteristics of PN Junction Diode
Applications of PN junction Diode
• PN junction diode in the reverse-biased configuration is
sensitive to light from a range between 400nm to
1000nm, which includes VISIBLE light. Therefore, it can
be used as a photodiode.
• It can also be used as a solar cell.
• P-N junction forward bias condition is used in all LED
lighting applications.
• The voltage across the P-N junction biased is used to
create Temperature Sensors, and Reference voltages.
• It is used in many circuits’ rectifiers, varactors
for voltage-controlled oscillators.
Real life applications
• Chargers: Your mobile charger is actually a rectifier(converts AC to DC).
Every type of rectifier is made up of diodes.
• AM/FM Radio: Diode is a vital component in AM/FM receiver. They are
used in separating the message signal from the modulating
signal(commonly known as demodulation).
• Noise reduction mic found in smartphones: The noise reductions mics
are basically clipping circuits and they are made up of diodes.
• In some external power sources it is important to keep the flow of
current in a single direction. Since diodes are unidirectional devices
they come in handy in these power supplies. Ex: UPS
Real life applications
• Solar panels: Solar panels use a special type of diode called the
photodiode. In simple terms, photodiodes convert light energy into
electrical energy. In electronic terms, when light is incident on the
surface of a photodiode it is forward biased and hence current
flows through it which in turn charges the solar cell.
• On/Off indicators: LEDs are used in almost every electronic gadget
as an on/off indicator. LEDs convert electrical energy into light
energy. In electronic terms, LEDs emit light when they are forward
biased. Ex: TV, Set top box, Notification indicators in smartphones
• Displays: Again, an array of LEDs are used as displays in
smartphones, TVs, Monitors, digital display boards. Ex: OLED,
AMOLED, POLED.
• LASER: LASERs find application in laser printers, CD/DVD players to
read/write data, optical fiber communication(without which
superfast internet these days would be impossible).
Real life applications
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Mobile charger: It is used as rectifier
Mosquito repellant, as rectifier to glow led
In soldering iron as rectifier
In battery charging systems, to protect from
reverse polarity
• Used in anti-parallel with inductive load to
eliminate back-emf
Real life applications
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Diodes can be used as rectifiers
Signal limiters
Voltage regulators
Switches
Signal modulators
Signal mixers
Signal demodulators and oscillators.
PN junction diode - some important
applications
• PN junction diode is used as a more triple, voltage doubler and
quadruples in voltage multiplier circuit.
• They are used as a switch in many electronics circuits.
• They are used in power supply.
• This diode can be used by many circuits rectifiers, varactor for
voltage-controlled oscillators.
• While PN junction diode produced light when biased with a current,
so it is used in light-emitting diode application.
• This diode can be also used for another diode called a light
amplification stimulation emission of radiation.
• In power electronics engineering, it can be used in solar cells.
• It used in the detector as well as the demodulator circuit so it can
be used as a detector for the demodulation circuit.
PN junction diode - some important
applications
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In digital electronics, this diode can be used as switches in digital logic design.
It can be used in PN junction photodiodes applications.
This diode can be used as a rectifier in the DC power supply.
While we are using the clipping circuit, this diode can be used to clip the portion of
AC.
They are used as clamper to change the reference voltage.
Zener diode most commonly used in stabilizing circuits.
It can be used as a varactor diode for use in the voltage-controlled tunning circuit
as may be found in radio and TV receivers.
The voltage across the PN junction biased is used to create temperature sensors
and reference voltages.
This diode can be used as voltage multipliers to increase the output voltage.
It can be used as a signal diode in communication circuits.
These diodes must be used in various daily life applications like computers, radios,
radars as wave shaping circuits.
It is used in many circuits or diode-like, a switching diode, Zener diode, PIN photodiode, varactor diode.
PN Junction Diode Summary
• Semiconductors contain two types of mobile charge
carriers, “Holes” and “Electrons”.
• The holes are positively charged while the electrons
negatively charged.
• A semiconductor may be doped with donor impurities
such as Antimony (N-type doping), so that it contains
mobile charges which are primarily electrons.
• A semiconductor may be doped with acceptor
impurities such as Boron (P-type doping), so that it
contains mobile charges which are mainly holes.
• The junction region itself has no charge carriers and is
known as the depletion region.
PN Junction Diode Summary
• The junction (depletion) region has a physical
thickness that varies with the applied voltage.
• When a diode is Zero Biased no external
energy
source
is
applied
and
a
natural Potential Barrier is developed across a
depletion layer which is approximately 0.5 to
0.7v for silicon diodes and approximately 0.3
of a volt for germanium diodes.
PN Junction Diode Summary
• When a junction diode is Forward Biased the
thickness of the depletion region reduces and
the diode acts like a short circuit allowing full
current to flow.
• When a junction diode is Reverse Biased the
thickness of the depletion region increases
and the diode acts like an open circuit
blocking any current flow, (only a very small
leakage current).
Semiconductor Devices - Silicon
Usually, silicon is used for making
semiconductor devices due to their
• High voltage rating
• Greater current and
• Less temperature sensitivity.
the
Bipolar Junction Transistor (BJT)
Has wide applicability in electronic equipment
include
• Mobile phones
• Industrial control
• Television and
• Radio transmitters.
Diode
Types of Diodes
Types of Diodes
Diode circuit symbol and physical
diode orientation
PN Junction diode Characteristics
Comparison with Silicon, Germanium,
and Gallium Arsenide
Rectifiers
• Convert AC into DC
Rectifiers - Rectification
• Most popular application of diode: Rectification
• Rectification - conversion of alternating current
(AC) to direct current (DC).
• Two types :
– Half wave rectifier
– Full wave rectifier
HWR
Circuit Diagram of HWR
Operation of Half Wave Rectifier
Half-Wave Rectification
Half-wave rectifier application: Two level lamp dimmer.
Half Wave Rectifier (HWR)
• When AC supply is applied at the input,
positive half cycle appears across the load,
• The negative half cycle is suppressed.
• The diode allows the current to flow only in
one direction.
• Thus the ac voltage is converted into dc
voltage.
Half Wave Rectifier (HWR)
• AC supply to be rectified is generally given
through a transformer.
• The transformer steps down or steps up the
main supply voltage as per the requirement.
• It also isolates the rectifier from power lines
and thus reduces the risk of electric shock.
Disadvantages of the Half Wave
Rectifier
• Output is low because AC supply delivers
power only half of the time.
• Output contains more alternating component
(ripples).
• Therefore, it needs heavy filter circuit to
smooth out the output.
Full Wave Rectifier (FWR)
• For both half cycles of the input (i.e., positive as
well as negative), output current flows through
the load in the same direction.
• Uses two diodes or 4 diodes.
• The two diodes conduct the current alternately.
2 types :
Center tapped full wave rectifier
Full Wave Bridge Rectifier
Center Tapped Full Wave Rectifier
• Employs a transformer with the secondary
winding AB tapped at the center point C.
FWR
Center Tapped FWR - Operation
FWR –
Output
Waveforms
Advantages and Disadvantages of
Center Tapped FWR
• Output and efficiency are high as the input AC
supply delivers power during the both of its
half cycles.
Disadvantages:
• It is difficult to locate the center on the
secondary for the tapping.
• The diode undergoes high peak inverse
voltage.
Full Wave Bridge Rectifier
Full Wave Bridge Rectifier – During
Positive Half Cycle
Full Wave Bridge Rectifier – During
Negative Half Cycle
FWR –
Output
Waveforms
Advantages of Full Wave Bridge
Rectifier
• Center tap transformer is eliminated.
• The peak inverse voltage across each diode is
one-half of the center tap circuit of the diode.
Disadvantages :
• Needs four diodes
Full-Wave Rectifiers
center-tap design
Positive Half-Cycle
Negative Half-Cycle
Disadvantages
• Necessity of a transformer with a centertapped secondary winding.
• For high power applications, the size and
expense of a suitable transformer is
significant.
• Consequently, the center-tap rectifier design is
only seen in low-power applications.
Full-Wave Bridge Rectifiers
Full-wave bridge rectifier: Current flow
for positive half-cycles.
Full-wave bridge rectifier: Current flow
for negative half-cycles.
Comparison
Types of Clipper Circuits
1. Series Positive Clipper
2. Series Negative Clipper
3. Shunt Positive Clipper
4. Shunt Negative Clipper
5. Series Positive Clipper with Positive Bias Voltage
6. Series Positive Clipper with Positive Bias Voltage Connected in Series
7. Series Positive Clipper with Negative Bias Voltage
8. Series Positive Clipper with Negative Bias Voltage Connected in Series
9. Series Negative Clipper with Positive Bias Voltage
10. Series Negative Clipper with Positive Bias Voltage Connected in Series
11. Series Negative Clipper with Negative Bias Voltage Connected in Parallel
12. Series Negative Clipper with Negative Bias Voltage Connected in Series
13. Shunt Positive Clipper with Positive Shunt Bias Voltage
14. Shunt Positive Clipper with Negative Shunt Bias Voltage
15. Shunt Negative Clipper with Positive Bias Voltage
16. Clipping Both Half Wave Cycles
Series positive clipper
with positive bias
During positive half cycle:
• Initially, the input supply voltage Vi is less than the battery
voltage VB (Vi < VB). So the battery voltage dominates the
input supply voltage. Hence, the diode is forward biased by
the battery voltage and allows electric current through it.
As a result, the signal appears at the output.
• When the input supply voltage Vi becomes greater than the
battery voltage VB, the diode D is reverse biased. So no
current flows through the diode. As a result, input signal
does not appear at the output.
• Thus, the clipping (removal of a signal) takes place during
the positive half cycle only when the input supply voltage
becomes greater than the battery voltage.
Series positive
clipper with
positive bias
• During the negative half cycle, terminal A is negative and terminal B
is positive.
• That means the diode D is forward biased due to the input supply
voltage.
• Furthermore, the battery is also connected in such a way that the
positive terminal is connected to p-side and the negative terminal is
connected to n-side.
• So the diode is forward biased by both battery voltage VB and input
supply voltage Vi.
• That means, during the negative half cycle, it doesn’t matter
whether the input supply voltage is greater or less than the battery
voltage, the diode always remains forward biased.
• So the complete negative half cycle appears at the output.
Series positive clipper with negative
bias
Series positive
clipper with
negative bias
During positive half cycle:
• During the positive half cycle, the diode D is
reverse biased by both input supply voltage
Vi and battery voltage VB.
• So no signal appears at the output during the
positive half cycle.
• Therefore, the complete positive half cycle is
removed.
Series positive
clipper with
negative bias
During negative half cycle:
• During the negative half cycle, the diode is forward
biased by the input supply voltage Vi and reverse
biased by the battery voltage VB.
• However, initially, the battery voltage VB dominates the
input supply voltage Vi.
• So the diode remains to be reverse biased until the
Vi becomes greater than VB.
• When the input supply voltage Vi becomes greater
than the battery voltage VB, the diode is forward biased
by the input supply voltage Vi.
• So the signal appears at the output.
Negative Clipper
Series negative clipper with positive
bias
Series negative
clipper with
positive bias
• During the positive half cycle, terminal A is positive and
terminal B is negative.
• That means the positive terminal A is connected to p-side
and the negative terminal B is connected to n-side.
• As we already know that if the positive terminal is
connected to p-side and the negative terminal is connected
to n-side then the diode is said to be forward biased.
• However, we are also supplying the voltage from another
source called battery.
• As shown in the figure, the positive terminal of the battery
is connected to n-side and the negative terminal of the
battery is connected to p-side of the diode.
Series negative
clipper with
positive bias
• That means the diode is forward biased by input supply
voltage Vi and reverse biased by battery voltage VB.
• Initially, the battery voltage is greater than the input
supply voltage.
• Hence, the diode is reverse biased and does not allow
electric current.
• Therefore, no signal appears at the output.
• When the input supply voltage Vi becomes greater
than the battery voltage VB, the diode is forward biased
and allows electric current.
• As a result, the signal appears at the output.
Series negative
clipper with
positive bias
During negative half cycle:
• During the negative half cycle, the diode is
reverse biased by both input supply voltage
Vi and battery voltage VB.
• So it doesn’t matter whether the input supply
voltage is greater or less than the battery voltage
VB, the diode always remains reverse biased.
• Therefore, during the negative half cycle, no
signal appears at the output.
Series negative clipper with negative
bias
Series negative
clipper with
negative bias
During positive half cycle:
• During the positive half cycle, the diode D is
forward biased by both input supply voltage
Vi and the battery voltage VB.
• So it doesn’t matter whether the input supply
voltage is greater or less than battery voltage
VB, the diode always remains forward biased.
• Therefore, during the positive half cycle, the
signal appears at the output.
Series negative
clipper with
negative bias
During negative half cycle:
• During the negative half cycle, the diode D is reverse
biased by the input supply voltage Vi and forward
biased by the battery voltage VB.
• Initially, the input supply voltage Vi is less than the
battery voltage VB.
• So the diode is forward biased by the battery voltage
VB. As a result, the signal appears at the output.
• When the input supply voltage Vi becomes greater
than the battery voltage VB, the diode will become
reverse biased.
• As a result, no signal appears at the output.
Positive Clipper
In shunt clipper, the diode is connected in parallel with the output load resistance.
Shunt positive
clipper with
positive bias
• During the positive half cycle, the diode is
forward biased by the input supply voltage Vi and
reverse biased by the battery voltage VB.
However, initially, the input supply voltage Vi is
less than the battery voltage VB. Hence, the
battery voltage VB makes the diode to be reverse
biased. Therefore, the signal appears at the
output. However, when the input supply voltage
Vi becomes greater than the battery voltage VB,
the diode D is forward biased by the input supply
voltage Vi. As a result, no signal appears at the
output.
Combinational Clipper
Combinational Clipper
Dual (combination)
clipper
• During the positive half cycle, the diode D1 is forward biased by the
input supply voltage Vi and reverse biased by the battery voltage
VB1.
• On the other hand, the diode D2 is reverse biased by both input
supply voltage Vi and battery voltage VB2.
• Initially, the input supply voltage is less than the battery voltage.
• So the diode D1 is reverse biased by the battery voltage VB1.
• Similarly, the diode D2 is reverse biased by the battery voltage VB2.
• As a result, the signal appears at the output.
• However, when the input supply voltage Vi becomes greater than
the battery voltage VB1, the diode D1 is forward biased by the input
supply voltage.
• As a result, no signal appears at the output.
Dual (combination)
clipper
• During the negative half cycle, the diode D1 is reverse biased
by both input supply voltage Vi and battery voltage VB1.
• On the other hand, the diode D2 is forward biased by the
input supply voltage Vi and reverse biased by the battery
voltage VB2.
• Initially, the battery voltage is greater than the input supply
voltage.
• Therefore, the diode D1 and diode D2 are reverse biased by
the battery voltage.
• As a result, the signal appears at the output.
• When the input supply voltage becomes greater than the
battery voltage VB2, the diode D2 is forward biased.
• As a result, no signal appears at the output.
Applications of clippers
• Clippers are commonly used in power
supplies.
• Used in TV transmitters and Receivers
• They are employed for different wave
generation such as square, rectangular, or
trapezoidal waves.
• Series clippers are used as noise limiters in FM
transmitters.
Positive Bias Diode Clipping
Diode Clipping of Different Bias levels
• When the voltage of the positive half cycle reaches
+4.7 V, diode D1 conducts and limits the waveform at
+4.7 V.
• Diode D2 does not conduct until the voltage reaches
–6.7 V.
• Therefore, all positive voltages above +4.7 V and
negative voltages below –6.7 V are automatically
clipped.
Diode Clampers - Types
1. Negative Clamper
2. Negative Clamper with Positive Reference
Voltage
3. Negative Clamper with Negative Reference
Voltage
4. Positive Clamper
5. Positive Clamper with Positive Reference Voltage
6. Positive Clamper with Negative Reference
Voltage
Positive Clamper Circuit
• A Clamping circuit restores the DC level.
• When a negative peak of the signal is raised above to the
zero level, then the signal is said to be positively clamped.
V0=Vi+Vm
Positive Clamper with Positive Vr
Positive Clamper with Negative Vr
Negative Clamper
• During the positive half cycle, the capacitor gets charged to its peak value vm.
• The diode is forward biased and conducts.
• During the negative half cycle, the diode gets reverse biased and gets open
circuited.
• The output of the circuit at this moment will be V0=Vi+Vm
Negative clamper with positive Vr
Negative Clamper with Negative Vr
Applications of Clippers &
Clampers
Clippers
• In television receiver for separating synchronizing
signals from composite picture signals
• In television transmitters at the time of processing
the picture signals.
• In generation of trapezoidal, square or rectangular
waves.
• As noise limiters in FM transmitters by clipping
excessive noise peaks above a specified level.
Clippers
• As voltage limiters and amplitude selectors
Circuit protection against Transients
• When a transient takes place on the input line,
diode D2 gets forward biased and starts
conducting.
• Thus transient is shorted to ground and the
circuit is protected from damage due to
transient.
Clampers (Direct Current restorers)
• To remove variable frequency interference in
television receivers, and in FM transmitters.
• In complex transmitter and receiver circuitry of
television - as a base line stabilizer to define
sections of the luminance signals.
• They clamp the wave forms to a fixed dc
potential.
• In test equipment, sonar and radar systems.
• In protection of the amplifiers from large errant
signals.
• To remove distortions
Applications of clamping circuits
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Sonar and radar testing
Used as voltage doublers
Used to remove distortions in a circuit
Used in video processing equipment like TV
Applications of Clippers & Clampers
Clippers
• Used for the generation and shaping of waveforms
• Used for the protection of circuits from spikes
• Used for amplitude restorers
• Used as voltage limiters
• Used in television circuits
• Used in FM transmitters
Clampers
• Used as direct current restorers
• Used to remove distortions
• Used as voltage multipliers
• Used for the protection of amplifiers
• Used as test equipment
• Used as base-line stabilizer
Other Diode Circuits - Voltage Doubler
Regulated Power Supply (RPS)
• Converts unregulated AC (alternating current)
to a constant DC (direct current).
• Used to ensure that the output remains
constant even if the input changes.
• Also known as a linear power supply
Regulated Power Supply
Regulated Power Supply
Regulation
• Last block in a regulated DC power supply.
• Output voltage or current will change or fluctuate
when there is a change in the input from ac mains or
due to change in load current at the output of the
regulated power supply or due to other factors like
temperature changes.
• Regulator maintains the output constant even when
changes at the input or any other changes occur.
• Transistor series regulator, fixed and variable IC
regulators or a Zener diode operated in the Zener
region can be used depending on their applications.
What is the Diode Current Equation?
• It expresses the relationship between the current
flowing through the diode as a function of the
voltage applied across it.
Where,
• I is the current flowing through the diode
• I0 is the dark saturation current,
• q is the charge on the electron,
• V is the voltage applied across the diode,
• η is the (exponential) ideality factor.
• K is the Boltzmann constant
• T is the absolute temperature in Kelvin.