Analog and Digital Electronics(EEC-309)
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Transcript of Analog and Digital Electronics(EEC-309)
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Analog and DigitalElectronics(EEC-309)
Nisha Prakash
(ECE Department)
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EEC-309 : ANALOG AND DIGITAL ELECTRONICS
ANALOG ELECTRONICS:
UNIT-ISpecial Diodes-
LED, Varactor diode, Photo diode, Schottky diode, Tunneldiode; their characteristics and applications. Transistors as aswitch.
UNIT-II
Frequency Response:Amplifier transfer function, low and high frequency response of
common emitter and common source amplifiers.
Feedback:
General feedback structure; properties of negative feedback;series-series, series-shunt, shunt-series and shunt-shuntfeedback amplifiers.
UNIT-III:
Basic principle of sinusoidal oscillator, R-C Phase Shift andWein Bridge oscillators, tuned oscillators- Collpits andHartley; Crystal oscillator
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DIGITAL ELECTRONICS:
UNIT-IV
Combinational Logic Circuits:Multiplexers/Demultiplexures,
Encoders/Decoders.Sequential Logic Circuits: latches, flip-flops- S-R, T, D, J-K.
Shift Registers: Basic principle, serial and parallel data transfer,shift left/right registers, universal shift register.
Counters: Mode N Counters, ripple counters, synchronouscounters, ring/Johnson counters.
UNIT-V
OP-AMP applications - Astable,Monostable and Bistablemultivibrators, Schmitt trigger, IC-
555 Timer, A/D and D/A converters.
Voltage Regulators: Series, shunt and switching regulators, op-amp based configurations.
Memories: Introduction to ROM, RAM; Sequential Memory,Memory organization.
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Text books
A.S. Sedra and K.C. Smith Microelectronics Circuits OxfordUniversity Press ( India)
Malvino & Leach, Digital Principles and applications Tata Mc.Graw Hill
R.A. Gayakwad Op amps and Linear Integrated Circuits PrenticeHall of India.
Balbir Kumar and Shail B.Jain, Electronic Devices and CircuitsPrentice Hall of India,2007
Reference books
Taub & Schilling Digital Electronics- TataMc Graw Hill
Anil K. Maini, Digital Electronics: Principles and Integrated circuitsWiley India Ltd,2008.
Millman, J. and Grabel A, MicroelectronicsMc Graw Hill
Anand Kumar, Switching Theory and Logic Design Prentice Hall ofIndia, 2008.
Aloke. K. Dutta, Semiconductor Devices and circuits, OxfordUniversity Press, 2008.
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UNIT-1
Special Diodes
Basics of semiconductor diode
If we join a section of N-type semiconductor material with a similar
section of P-type semiconductor material, we obtain a device known
as a PN JUNCTION.
The area where the N and P regions meet is appropriately called thejunction.
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How a pn junction diode
works? The most important property of a junction diode is its ability
to pass an electric current in one direction only.
When the p-type region of the p-n junction is connected to
the positive terminal of the battery, current will flow. Thediode is said to be underforward bias. However, when thebattery terminals are reversed, the p-n junction almostcompletely blocks the current flow. This is called reversebias.
If the diode is not connected at all, it is said to be open-circuitedand of course no current can flow through thediode.
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pn-junction diode-
characteristics
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BJT(BipolarJunction Transistor)
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A bipolar junction transistor consists of three regions of doped
semiconductors. A small current in the center or base regioncan be used to control a larger current flowing between the
end regions (emitter and collector). The device can be
characterized as a current amplifier, having many applications
foramplification and switching.
Transistor Operation
A transistor in a circuit will be in one of three conditions
Cut off (no collector current), useful forswitch operation.
In the active region (some collector current, more than a few tenths
of a volt above the emitter), useful foramplifierapplications
In saturation (collector a few tenths of a volt above emitter), large
current useful for "switch on" applications.
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LEDFunction
LEDs emit light when an electric current passesthrough them.
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In a forward-biased pn junction diode, within the structure andmainly close to junction, a recombination of holes & e- occurs.
This recombination requires that the energy possessed by
unbound free e- be transferred to another state. In allsemiconductors p-n junctions are some of the energy is givenoff in the form of heat or some in forms of photons.
The recombination of injected carriers are due to forward-biased junctions results in emitted light at the site ofrecombination.
Si & Ge diodes : Emits energy in form of HEAT So, GaAs diodes are used : Emits light in IR (invisible) zone
during recombination process.
Applications:
Security system
Industrial processing Optical coupling
Safety controls such as Garage-door openers, Homeentertainment centers, etc where the IR light of remote controlis the controlling element.
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Bargraph 7-segment Starburst Dot matrix
Relative Intensity vs Wavelength (P)
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Photodiode
Silicon photodiodes are semiconductor devices responsive to high
energy particles and photons. Photodiodes operate by absorption of photons or charged particles
and generate a flow of current in an external circuit, proportional to
the incident power.
Photodiodes can be used to detect the presence or absence of
minute quantities of light. The photodiode is a semiconductor pn junction device whose region
of operation is limited to reverse-bias region. They are usually made
of GaAs. It basically converts light signal into electrical signal.
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Applications: Silicon photodiodes are utilized in such diverse
applications
spectroscopy
photography
analytical instrumentation
optical position sensors
beam alignment
surface characterization
laser range finders
optical communications
medical imaging instruments.
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Planar diffused Silicon photodiode
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Dark current is the current that
exists at no applied potential.
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APPLICATIONS
In alarm system, the reverse current will continue to flow
as long as the light beam is not broken. If the beam is interrupted
Current drops to dark level and sounds the alarm.
Used in family of circuits like optoelectronics or photonics.
Used in optical signal processing, storage and transmission.
Fiber-optics transmission of Telephone and T.V. signals.
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Schottky Barrier diode
Schottky diode or Schottky barrier diode is an electroniccomponent that is widely used for radio frequency (RF)applications as a mixer and detector diode.
Also used in power application as rectifier, againbecause of low voltage drop leading to low level ofpower loss as compared to pn junction diode.
It is also called surface barrier, hot-carrier or hot-electron
diode.
It is one of the oldest semiconductor device.
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Structure Most simple is the point contact diode where a metal wire is pressed
against a clean semiconductor surface.
They were found to be very unreliable, requiring frequent
repositioning of the wire to ensure satisfactory operation.
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Operation
Its construction is different from normal pn junction diode,
In this a metal semiconductor junction is created.
In both materials, e- is majority carriers when materials are
joined, the e- in n-type semiconductors material immediately
flow into adjoining metal, establishing a heavy flow of majority
carriers (e-).
Since the injected carriers have a high K.E. level compared to
the e- of metal, they are called HOT-CARRIERS.
Schottky diodes are unique in that conduction is entirely by
majority carriers.
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Applications
Mainly in switching power supplies.
The Schottky barrier diodes are widely used in the electronics
industry finding many uses as diode rectifier. Its unique properties
enable it to be used in a number of applications where other diodes
would not be able to provide the same level of performance. In
particular it is used in areas including:
RF mixer and detector diode
Power rectifier
Power OR circuits
Solar cell applications Clamp diode - especially with its use in LS TTL
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Tunnel Diode
In 1958, Leo Esaki, a Japanese scientist, discovered that if a
semiconductor junction diode is heavily doped with impurities,
it will have a region of negative resistance.
This is a germanium semiconductor diode that uses a quantum
mechanical tunneling effect to get very high switching speeds, to the
order of 5 GHz.
The normal junction diode uses semiconductor materials that arelightly doped with one impurity atom for ten-million semiconductor
atoms. This low doping level results in a relatively wide depletion
region. Conduction occurs in the normal junction diode only if the
voltage applied to it is large enough to overcome the potential
barrier of the junction. The tunnel diode has a region in its voltage current characteristic
where the current decreases with increased forward voltage, known
as its negative resistance region. This characteristic makes the
tunnel diode useful in oscillators and as a microwave amplifier.
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In the TUNNEL DIODE, the semiconductor materials used in
forming a junction are doped to the extent of one-thousand
impurity atoms for ten-million semiconductor atoms. This
heavy doping produces an extremely narrow depletion zone
similar to that in the Zener diode.
Also because of the heavy doping, a tunnel diode exhibits an
unusual current-voltage characteristic curve as compared
with that of an ordinary junction diode. The characteristic
curve for a tunnel diode is illustrated in figure:
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The three most important aspects of this characteristic curve are
(1) the forward current increase to a peak (IP) with a small applied
forward bias,
(2) the decreasing forward current with an increasing forward bias to a
minimum valley current (IV), and
(3) the normal increasing forward current with further increases in the
bias voltage.
The portion of the characteristic curve between IP and IV is the region
ofnegative resistance.
Applications:
They are used in low power amplifiers; DLVA, microwave and RF
power monitors, high-frequency triggers, ALC loops, zero bias
detectors, ACP tunnel diode circuits, etc.
Since they are more resistant to nuclear radiation, tunnel diodes are
used in space applications like amplifiers for satellite communications.