analog and digital electronics(eec-309)

8/6/2019 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.

analog and digital electronics(eec-309)

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