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8/6/2019 Ece Acads Related interviews for I.T MBA B.TECH

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Bubble sort is a simple sorting algorithm. It works by repeatedly stepping through the

list to be sorted, comparing two items at a time and swapping them if they are in the

wrong order. The pass through the list is repeated until no swaps are needed, which

indicates that the list is sorted. The algorithm gets its name from the way smaller

elements "bubble" to the top of the list. Because it only uses comparisons to operate

on elements, it is a comparison sort.

Step-by-step exampleLet us take the array of numbers "5 1 4 2 8", and sort the array from lowest number to greatest number

using bubble sort algorithm. In each step, elements written in bold are being compared.

First Pass:( 51 4 2 8 ) ( 15 4 2 8 ) Here, algorithm compares the first two elements, and swaps them.

( 1 54 2 8 ) ( 1 45 2 8 )

( 1 4 52 8 ) ( 1 4 25 8 )

( 1 4 2 58 ) ( 1 4 2 58 ) Now, since these elements are already in order, algorithm does not swap

them.

Second Pass:( 14 2 5 8 ) ( 14 2 5 8 )

( 1 42 5 8 ) ( 1 24 5 8 )

( 1 2 45 8 ) ( 1 2 45 8 )

( 1 2 4 58 ) ( 1 2 4 58 )

Now, the array is already sorted, but our algorithm does not know if it is completed. Algorithm needsone whole pass without any swap to know it is sorted.

Third Pass:( 12 4 5 8 ) ( 12 4 5 8 )

( 1 24 5 8 ) ( 1 24 5 8 )

( 1 2 45 8 ) ( 1 2 45 8 )

( 1 2 4 58 ) ( 1 2 4 58 )

Finally, the array is sorted, and the algorithm can terminate...

Selection sort is a simple sorting algorithm that improves on the performance of

bubble sort. It works by first finding the smallest element using a linear scan and

swapping it into the first position in the list, then finding the second smallest element

by scanning the remaining elements, and so on. Selection sort is unique compared to

almost any other algorithm in that its running time is not affected by the priorordering of the list: it performs the same number of operations because of its simple

structure. Selection sort requires (n - 1) swaps and hence (n) memory writes.

However, Selection sort requires (n - 1) + (n - 2) + ... + 2 + 1 = n(n - 1) / 2 = (n2)

comparisons. Thus it can be very attractive if writes are the most expensive operation,

but otherwise selection sort will usually be outperformed by insertion sort or the more

complicated algorithms.

Insertion sort is a simple sorting algorithm that is relatively efficient for small lists

and mostly-sorted lists, and often is used as part of more sophisticated algorithms. It

works by taking elements from the list one by one and inserting them in their correct

position into a new sorted list. In arrays, the new list and the remaining elements can

share the array's space, but insertion is expensive, requiring shifting all followingelements over by one. The insertion sort works just like its name suggests - it inserts

each item into its proper place in the final list. The simplest implementation of this

requires two list structures - the source list and the list into which sorted items are

inserted. To save memory, most implementations use an in-place sort that works by

moving the current item past the already sorted items and repeatedly swapping it with

the preceding item until it is in place.


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Sorting is typically done in-place. The resulting array after k iterations contains the

first kentries of the input array and is sorted. In each step, the first remaining entry of

the input is removed, inserted into the result at the right position, thus extending the

result:

becomes:

with each element >x copied to the right as it is compared againstx.

A binary search algorithm (or binary chop) is a technique for finding a particular

value in a sorted list. It makes progressively better guesses, and closes in on thesought value by selecting the median element in a list, comparing its value to the

target value, and determining if the selected value is greater than, less than, or equal to

the target value. A guess that turns out to be too high becomes the new top of the list,

and a guess that is too low becomes the new bottom of the list. Pursuing this strategy

iteratively, it narrows the search by a factor of two each time, and finds the target

value.

Object-oriented programming (OOP) is a programming paradigm that uses

"objects" and their interactions to design applications and computer programs. It is

based on several techniques, including encapsulation, modularity, polymorphism, and

inheritance. It was not commonly used in mainstream software application

development until the early 1990s. Many modern programming languages now

support OOP

Continuous function is a function for which, intuitively, small changes in the input

result in small changes in the output. Otherwise, a function is said to be

discontinuous. A continuous function with a continuous inverse function is called

bicontinuous. An intuitive though imprecise (and inexact) idea of continuity is given

by the common statement that a continuous function is a function whose graph can be

drawn without lifting the chalk from the blackboard. ifM(t) denotes the amount of

money in a bank account at time t, then the function jumps whenever money is

deposited or withdrawn, so the functionM(t) is discontinuous.

the standard deviation of a probability distribution, random variable, or population

or multiset of values is a measure of the spread of its values. The standard deviation is

usually denoted with the letter (lower case sigma). It is defined as the square root of

the variance. The standard deviation is the most common measure of statistical

dispersion, measuring how widely spread the values in a data set are. If many data

points are close to the mean, then the standard deviation is small; if many data points

are far from the mean, then the standard deviation is large. If all the data values are

equal, then the standard deviation is zero.


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normal distribution, also called the Gaussian distribution, is an important family of

continuous probability distributions, applicable in many fields. Each member of the

family may be defined by two parameters, location and scale: the mean ("average", )

and variance (standard deviation squared) 2, respectively. The standard normal

distribution is the normal distribution with a mean of zero and a variance of one.

correlation, (often measured as a correlation coefficient) , indicates the strength and

direction of a linear relationship between two random variables.

Isotopes are any of the different forms of an element each having different atomic

mass (mass number). Isotopes of an element have nuclei with the same number of

protons (the same atomic number) but different numbers of neutrons. Therefore,

isotopes have different mass numbers, which give the total number of nucleonsthe

number of protons plus neutrons. (Uranium-235 Uranium-238)

LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.

A typical laser emits light in a narrow, low-divergence monochromatic (single-

coloured, if the laser is operating in the visible spectrum), beam with a well-defined

wavelength. In this way, laser light is in contrast to a light source such as the

incandescent light bulb, which emits light over a wide area and over a wide spectrum

of wavelengths.

Laser consists of a gain medium inside a highly reflective optical cavity, as

well as a means to supply energy to the gain medium. The gain medium is a material

(gas, liquid, solid or free electrons) with appropriate optical properties. In its simplestform, a cavity consists of two mirrors arranged such that light bounces back and forth,

each time passing through the gain medium. Typically, one of the two mirrors, the

output coupler, is partially transparent. The output laser beam is emitted through this

mirror. Light of a specific wavelength that passes through the gain medium is

amplified; the surrounding mirrors ensure that most of the light makes many passes

through the gain medium, stimulating the gain material continuously. Part of the light

that is between the mirrors, passes through the partially transparent mirror and

escapes as a beam of light.

The process of supplying the energy required for the amplification is called pumping.

The energy is typically supplied as an electrical current or as light at a different

wavelength. A typical pump source is a flash lamp or perhaps another laser. Most

practical lasers contain additional elements that affect properties such as thewavelength of the emitted light and the shape of the beam.

Zeroth law of thermodynamics If two thermodynamic systems are in thermal

equilibrium with a third, they are also in thermal equilibrium with each other.

First law of thermodynamics for a thermodynamic cycle the sum of net heat

supplied to the system and the net work done by the system is equal to zero.( energy

cannot be created or destroyed)


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Second law of thermodynamics is an expression of the universal law of increasing

entropy, stating that the entropy of an isolated system which is not in equilibrium will

tend to increase over time, approaching a maximum value at equilibrium. (In an

isolated system, a process can occur only if it increases the total entropy of the

system.)

Third law of thermodynamics As a system approaches absolute zero, all processes

cease and the entropy of the system approaches a minimum value. It can be concluded

as 'If T=0K, then S=0' where T is the temperature of a closed system and S is the

entropy of the system.

Newton's laws of motionFirst law: law of inertia "An object will stay at rest or continue at a constant velocity

unless acted upon by an external unbalanced force".

Second law: the net force on a particle is proportional to the time rate of change of its

linear momentum: F = d[mv] / dt. Momentum is the product of mass and velocity.

When the mass is constant, this law is often stated as F = ma (the net force on an

object is equal to the mass of the object multiplied by its acceleration).Third law: "Every action has an equal and opposite reaction".

Calorie is a unit heat: the amount of heat required to raise the temperature of a gram

of water by 1 C (from 14.5 C to 15.5 C)

One joule is the work done, or energy expended, by a force of one newton moving

one meter along the direction of the force. This quantity is also denoted as a newton

metre with the symbol Nm.

Cache Memory: A CPU cache is a cache used by the central processing unit of a

computer to reduce the average time to access memory. The cache is a smaller, faster

memory which stores copies of the data from the most frequently used main memory

locations. As long as most memory accesses are to cached memory locations, the

average latency of memory accesses will be closer to the cache latency than to the

latency of main memory.

What do you mean by engineering?Most simply, the art of directing the great sources of power in nature for the use and

the convenience of people.

The application of scientific and mathematical principles to practical ends such as the

design, manufacture, and operation of efficient and economical structures, machines,

processes, and systems.

What do you mean by telecommunicationThe science and technology of communication at a distance by electronic

transmission

What is electronics?elctron+dynamics is electronics,means this is a study of the behaviour(dynamic) of

electrons in semi conductors.

What is electrical?


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Any thing Related to or associated with electricity.

What is the difference between the terms Electrical and Electronics?Electrical relates to the development and delivery of the electrical energy to the

various devices that perform specific functions in a given environment. Example: The

alternator in your car that series of wires delivers electrical power / energy to various

components (radio, the computer that monitors / controls operation of the engine) intodays cars.

Where as "Electronics" relates more to the complex functions performed

within a given device, more often now days by circuits comprised of many micro

electronic sub components that make up the structure of a single micro electronic

component. Example: a typical CPU chip would / could contain thousands of

individual transistor circuits within a device no bigger that the size of your small

finger nail with room to spare.

In Electronics we deal with voltages upto 20 volts and in electrical we have

voltages 110+, electronics uses DC only.

AC motor

An AC motor consists of two basic parts:* An outside stationary statorhaving coils supplied with AC current to produce a

rotating magnetic field, and;

* An inside rotorattached to the output shaft that is given a torque by the rotating

field.

There are two types of AC motors, depending on the type of rotor used:

* The synchronous motor, which rotates exactly at the supply frequency or a

submultiple of the supply frequency. The magnetic field on the rotor is either due to

current transported with slip rings or a permanent magnet.

* The induction motor, which turns slightly slower than the supply frequency. The

magnetic field on the rotor of this motor is created by an induced current.

Three-phase AC induction motors

the three-phase (or polyphase) AC induction motor is commonly used especially for

higher-powered motors. The phase differences between the three phases of the

polyphase electrical supply create a rotating electromagnetic field in the motor.

Through electromagnetic induction, the rotating magnetic field induces a

current in the conductors in the rotor, which in turn sets up a counterbalancing

magnetic field that causes the rotor to turn in the direction the field is rotating. The

rotor must always rotate slower than the rotating magnetic field produced by the

polyphase electrical supply; otherwise, no counterbalancing field will be produced in

the rotor tough, the motor continuously tries to reach the speed of the rotating

magnetic field.There are two types of rotors used in induction motors: squirrel cage rotors

and wound rotors.

Three-phase AC synchronous motors

If connections to the rotor coils of a three-phase motor are taken out on slip-rings and

fed a separate field current to create a continuous magnetic field (or if the rotor

consists of a permanent magnet), the result is called a synchronous motor because the

rotor will rotate in synchronism with the rotating magnetic field produced by the

polyphase electrical supply.


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Single-phase AC induction motors

Three-phase motors inherently produce a rotating magnetic field. However, when

only single-phase power is available, the rotating magnetic field must be produced

using other means. Several methods are commonly used:

Shaded-pole motor: A common single-phase motor is the shaded-pole motor, which is

used in devices requiring low starting torque, such as electric fans. In this motor,small single-turn copper "shading coils" create the moving magnetic field. Part of

each pole is encircled by a copper coil or strap; the induced current in the strap

opposes the change of flux through the coil (Lenz's Law), so that the maximum field

intensity moves across the pole face on each cycle, thus producing a low level rotating

magnetic field which is large enough to turn both the rotor and its attached load. As

the rotor accelerates the torque builds up to its full level as the principal (rotationally

stationary) magnetic field is rotating relative to the rotating rotor. Such motors are

difficult to reverse without significant internal alterations.

Split-phase induction motor: Another common single-phase AC motor is the split-

phase induction motor, commonly used in major appliances such as washing

machines and clothes dryers. Compared to the shaded pole motor, these motors can

generally provide much greater starting torque by using a special startup winding inconjunction with a centrifugal switch.

In the split-phase motor, the startup winding is designed with a higher

resistance than the running winding. This creates an LR circuit which slightly shifts

the phase of the current in the startup winding. When the motor is starting, the startup

winding is connected to the power source via a set of spring-loaded contacts pressed

upon by the not-yet-rotating centrifugal switch. The starting winding is wound with

fewer turns of smaller wire than the main winding, so it has a lower inductance (L)

and higher resistance (R). The lower L/R ratio creates a small phase shift, not more

than about 30 degrees, between the flux due to the main winding and the flux of the

starting winding. The starting direction of rotation may be reversed simply by

exchanging the connections of the startup winding relative to the running winding..

The phase of the magnetic field in this startup winding is shifted from the

phase of the mains power, allowing the creation of a moving magnetic field which

starts the motor. Once the motor reaches near design operating speed, the centrifugal

switch activates, opening the contacts and disconnecting the startup winding from the

power source. The motor then operates solely on the running winding. The starting

winding must be disconnected since it would increase the losses in the motor.

Capacitor start motor: In a capacitor start motor, a starting capacitor is inserted in

series with the startup winding, creating an LC circuit which is capable of a much

greater phase shift (and so, a much greater starting torque). The capacitor naturally

adds expense to such motors.

Permanent split-capacitor motor: Another variation is the Permanent Split-Capacitor

(PSC) motor (also known as a capacitor start and run motor). This motor operatessimilarly to the capacitor-start motor described above, but there is no centrifugal

starting switch and the second winding is permanently connected to the power source.

PSC motors are frequently used in air handlers, fans, and blowers and other cases

where a variable speed is desired. By changing taps on the running winding but

keeping the load constant, the motor can be made to run at different speeds. Also

provided all 6 winding connections are available separately, a 3 phase motor can be

converted to a capacitor start and run motor by commoning two of the windings and

connecting the third via a capacitor to act as a start winding.


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DC MotorWhen a current passes through the coil wound around a soft iron core, the side of the

positive pole is acted upon by an upwards force, while the other side is acted upon by

a downward force. According to Fleming's left hand rule, the forces cause a turning

effect on the coil, making it rotate. To make the motor rotate in a constant direction,

"direct current" commutators make the current reverse in direction every half a cyclethus causing the motor to rotate in the same direction.

If the shaft of a DC motor is turned by an external force, the motor will act

like a generator and produce an Electromotive force (EMF). During normal operation,

the spinning of the motor produces a voltage, known as the counter-EMF (CEMF) or

back EMF, because it opposes the applied voltage on the motor. This is the same

EMF that is produced when the motor is used as a generator (for example when an

electrical load (resistance) is placed across the terminals of the motor and the motor

shaft is driven with an external torque). Therefore, the total voltage drop across a

motor consists of the CEMF voltage drop, and the parasitic voltage drop resulting

from the internal resistance of the armature's windings

The counter-emf aids the armature resistance to limit the current through the

armature. When power is first applied to a motor, the armature does not rotate. At thatinstant the counter-emf is zero and the only factor limiting the armature current, is the

armature resistance. Usually the armature resistance of a motor is less than one ohm;

therefore the current through the armature would be very large when the power is

applied. This current can make an excessive voltage drop affecting other equipment in

the circuit and even trip overload protective devices. Therefore the need arises for an

additional resistance in series with the armature to limit the current until the motor

rotation can build up the counter-emf. As the motor rotation builds up, the resistance

is gradually cut out.

Kirchhoff's Current Law (KCL):At any point in an electrical circuit where charge

density is not changing in time, the sum of currents flowing towards that point is

equal to the sum of currents flowing away from that point.

Kirchhoff's Voltage Law (KVL):The directed sum of the electrical potential

differences around a closed circuit must be zero.

Ohm's law states that in an electrical circuit, the current passing through a conductor

between two points is directly proportional to the potential difference (i.e. voltage

drop or voltage) across the two points, and the constant of proportionality is known as

resistance.

Why is ac transmission preferred over dc transmission?

Direct current (DC) is not in use in any power grid globally. This is because DC is tooexpensive to deliver over long distances. DC drops in power over distance, hence not

suitable for power grids.

Alternating current (AC) on the other hand is very efficient for long distances

and does not drop in power like the way DC does. Also, you can step up or step down

the voltage with AC current which you can't really do so with DC and its naturally

produced by generators

DC is used for small appliances and where safety is required. No one really

gets electricuted on DC current.


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So why is DC used?Its easy to produce at small levels using batteries, thus preferable in small devices.

Also all digital circuits work on DC

DIODE

The directionality of current flow most diodes possess is sometimes generically calledthe rectifying property. The most common function of a diode is to allow an electric

current to flow in one direction (called the forward biased condition) and to block it in

the opposite direction (the reverse biased condition).

V-I, characteristic curve is related to the transport of carriers through the so-

called depletion layer or depletion region that exists at the p-n junction between

differing semiconductors. When a p-n junction is first created, conduction band

(mobile) electrons from the N-doped region diffuse into the P-doped region where

there is a large population of holes (places for electrons in which no electron is

present) with which the electrons recombine. When a mobile electron recombines

with a hole, both hole and electron vanish, leaving behind an immobile positively

charged donor on the N-side and negatively charged acceptor on the P-side. The

region around the p-n junction becomes depleted of charge carriers and thus behavesas an insulator.

However, the depletion width cannot grow without limit. For each electron-

hole pair that recombines, a positively-charged dopant ion is left behind in the N-

doped region, and a negatively charged dopant ion is left behind in the P-doped

region. As recombination proceeds and more ions are created, an increasing electric

field develops through the depletion zone which acts to slow and then finally stop

recombination. At this point, there is a built-in potential across the depletion zone.

If an external voltage is placed across the diode with the same polarity as the built-in

potential, the depletion zone continues to act as an insulator preventing a significant

electric current. This is the reverse bias phenomenon. However, if the polarity of the

external voltage opposes the built-in potential, recombination can once again proceed

resulting in substantial electric current through the p-n junction. For silicon diodes,

the built-in potential is approximately 0.6 V. Thus, if an external current is passed

through the diode, about 0.6 V will be developed across the diode such that the P-

doped region is positive with respect to the N-doped region and the diode is said to be

turned on as it has a forward bias.


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IVcharacteristics of a P-N junction diode (not to scale).

A diodes IV characteristic can be approximated by four regions of operation (see

the figure at right).

At very large reverse bias, beyond the peak inverse voltage or PIV, a process called

reverse breakdown occurs which causes a large increase in current that usually

damages the device permanently. The avalanche diode is deliberately designed for use

in the avalanche region. In the Zener diode, the concept of PIV is not applicable. A

Zener diode contains a heavily doped p-n junction allowing electrons to tunnel from

the valence band of the p-type material to the conduction band of the n-type material,

such that the reverse voltage is clamped to a known value (called the Zener

voltage), and avalanche does not occur. Both devices, however, do have a limit to themaximum current and power in the clamped reverse voltage region.

The second region, at reverse biases more positive than the PIV, only a verysmall reverse saturation current flows. In the reverse bias region for a normal P-N

rectifier diode, the current through the device is very low (in the A range).

The third region is forward but small bias, where only a small forward current

is conducted.

As the potential difference is increased above an arbitrarily defined cut-in voltage or

on-voltage, the diode current becomes appreciable (the level of current considered

appreciable and the value of cut-in voltage depends on the application), and the

diode presents a very low resistance.

The currentvoltage curve is exponential. In a normal silicon diode at rated

currents, the arbitrary 'cut-in' voltage is defined as 0.6 to 0.7 volts. The value is

different for other diode types Schottky diodes can be as low as 0.2 V and red

light-emitting diodes (LEDs) can be 1.4 V or more and blue LEDs can be up to 4.0 V.At higher currents the forward voltage drop of the diode increases. A drop of

1v to 1.5v is typical at full rated current for power diodes.

Over-voltage protection: Diodes are frequently used to conduct damaging high

voltages away from sensitive electronic devices. They are usually reverse-biased

(non-conducting) under normal circumstances. When the voltage rises above the

normal range, the diodes become forward-biased (conducting). For example, diodes

are used in motor controller and relay circuits to de-energize coils rapidly without the


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damaging voltage spikes that would otherwise occur. (Any diode used in such an

application is called a flyback diode). Many integrated circuits also incorporate diodes

on the connection pins to prevent external voltages from damaging their sensitive

transistors. Specialized diodes are used to protect from over-voltages at higher power.

Transistor: Transistor. This is an abbreviated combination of the words

"transconductance" or "transfer", and "varistor". A transistor is a semiconductordevice, commonly used to amplify or switch electronic signals. Modern transistors are

divided into two main categories: bipolar junction transistors (BJTs) and field effect

transistors (FETs). Application of current in BJTs and voltage in FETs between the

input and common terminals increases the conductivity between the common and

output terminals, thereby controlling current flow between them. The transistor

characteristics depend on their type.

Bipolar junction transistor(BJT) was the first type of transistor to be mass-

produced. Bipolar transistors are so named because they conduct by using both

majority and minority carriers. The three terminals of the BJT are named emitter, base

and collector. Two p-n junctions exist inside a BJT: the base/emitter junction and

base/collector junction. "The [BJT] is useful in amplifiers because the currents at the

emitter and collector are controllable by the relatively small base current." In an NPNtransistor operating in the active region, the emitter-base junction is forward biased,

and electrons are injected into the base region. Because the base is narrow, most of

these electrons will diffuse into the reverse-biased base-collector junction and be

swept into the collector; perhaps one-hundredth of the electrons will recombine in the

base, which is the dominant mechanism in the base current. By controlling the

number of electrons that can leave the base, the number of electrons entering the

collector can be controlled

Unlike the FET, the BJT is a lowinput-impedance device. Also, as the base

emitter voltage (Vbe) is increased the baseemitter current and hence the collector

emitter current (Ice) increase exponentially according to the Shockley diode model

and the Ebers-Moll model. Because of this exponential relationship, the BJT has a

higher transconductance than the FET.

Bipolar transistors can be made to conduct by exposure to light, since

absorption of photons in the base region generates a photocurrent that acts as a base

current; the collector current is approximately beta times the photocurrent. Devices

designed for this purpose have a transparent window in the package and are called

phototransistors.

Silicon-controlled rectifier (Thyristor)(or semiconductor-controlled rectifier) is a 4-

layer solid state device that controls current flow.

An SCR (left) can be thought of as two BJT transistors working together (right).


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An SCR can be seen as a conventional rectifier controlled by a logic gate signal. It is a

4-layered, 3-terminal device. A p-type layer acts as an anode and an n-type layer as a

cathode; the p-type layer closer to the n-type(cathode) acts as a gate.

In the normal "off" state, the device restricts current flow to the leakage

current. When the gate to cathode voltage exceeds a certain threshold, the device turns

"on" and conducts current. The device will remain in the "on" state even after gate

current is removed so long as current through the device remains above the holdingcurrent. Once current falls below the holding current for an appropriate period of

time, the device will switch off.

If the applied voltage increases rapidly enough, capacitive coupling may

induce enough charge into the gate to trigger the device into the "on" state; this is

referred to as "dv/dt triggering." This is usually prevented by limiting the rate of

voltage rise across the device. "dv/dt triggering" may not switch the SCR into full

conduction rapidly and the partially-triggered SCR may dissipate more power than is

usual, possibly harming the device.

SCRs can also be triggered by increasing the forward voltage beyond their

rated breakdown voltage (also called as breakover voltage), but again, this does not

rapidly switch the entire device into conduction and so may be harmful so this mode

of operation is also usually avoided.

SCRs are used in power switching, phase control, chopper, battery chargers,

and inverter circuits. Industrially they are applied to produce variable DC voltages for

motors (from a few to several thousand HP) from AC line voltage.

Two SCRs in "inverse parallel" are often used in place of a TRIAC for

switching inductive loads on AC circuits. Because each SCR only conducts for half of

the power cycle and is reverse-biased for the other half-cycle, turn-off of the SCRs is

assured. By comparison, the TRIAC is capable of conducting current in both

directions and assuring that it switches off during the brief zero-crossing of currentflow can be difficult.

Doping refers to the process of intentionally introducing impurities into an extremely

pure (also referred to as intrinsic) semiconductor in order to change its electrical

properties. The impurities are dependent upon the type of semiconductor. Lightly and

moderately doped semiconductors are referred to as extrinsic. A semiconductor which

is doped to such high levels that it acts more like a conductor than a semiconductor is

called degenerate. Where many more are added (of the order of 1 in 10,000) then the


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doping is referred to as heavy, or high. This is often shown as n+ for n-type dopant or

p+ for p-type doping. By doping pure silicon with group V elements such as

phosphorus, extra valence electrons are added which become unbonded from

individual atoms and allow the compound to be electrically conductive, n-type

semiconductor. Doping with group III elements, such as boron, which are missing the

fourth valence electron creates "broken bonds", or holes, in the silicon lattice that are

free to move. This is electrically conductive, p-type semiconductor. In this contextthen, a group V element is said to behave as an electron donor, and a group III

element as an acceptor.

What is power electronics?

Power electronics is the technology associated with the efficient conversion, control

and conditioning of electric power by static means from its available input form into

the desired electrical output form.( modify voltage, current or frequency)

What is modulation?modulation is the process of varying a periodic waveform, in order to use that signal

to convey a message. Normally a high-frequency sinusoid waveform is used as carrier

signal. The three key parameters of a sine wave are its amplitude ("volume"), itsphase ("timing") and its frequency ("pitch"), all of which can be modified in

accordance with a low frequency information signal to obtain the modulated signal.

A device that performs modulation is known as a modulator and a device that

performs the inverse operation of modulation is known as a demodulator (sometimes

detector or demod). A device that can do both operations is a modem (short for

"MOdulate-DEModulate")). Analog and digital modulation facilitate frequency

division multiplex (FDM), where several low pass information signals are transferred

simultaneously over the same shared physical medium, using separate bandpass

channels.

What is a Cyclotron?

A cyclotron is a type of particle accelerator. Cyclotrons accelerate charged particles

using a high-frequency, alternating voltage (potential difference). A perpendicular

magnetic field causes the particles to spiral almost in a circle so that they re-encounter

the accelerating voltage many times.

In the cyclotron, a high-frequency alternating voltage applied across the "D"

electrodes (also called "dees") alternately attracts and repels charged particles. The

particles, injected near the center of the magnetic field, accelerate only when passing

through the gap between the electrodes. The perpendicular magnetic field (passing

vertically through the "D" electrodes), combined with the increasing energy of the

particles forces the particles to travel in a spiral path.

With no change in energy the charged particles in a magnetic field will follow

a circular path. In the Cyclotron, energy is applied to the particles as they cross thegap between the dees and so they are accelerated (at the typical sub-relativistic speeds

used) and will increase in mass as they approach the speed of light. Either of these

effects (increased velocity or increased mass) will increase the radius of the circle and

so the path will be a spiral.


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control system is a device or set of devices to manage, command, direct or regulate

the behaviour of other devices or systems.

Microprocessor: A device that integrates the functions of the central processing unit

(CPU) of a computer onto one semiconductor chip or integrated circuit (IC). In

essence, the microprocessor contains the core elements of a computer system, its

computation and control engine. Only a power supply, memory, peripheral interface

ICs, and peripherals (typically input/output and storage devices) need be added to

build a complete computer system. A microprocessor consists of multiple internal

function units. A basic design has an arithmetic logic unit, a control unit, a memoryinterface, an interrupt or exception controller, and an internal cache.

Microcontroller (also MCU or C) is a computer-on-a-chip. It is a type of

microprocessor emphasizing high integration, low power consumption, self-

sufficiency and cost-effectiveness, in contrast to a general-purpose microprocessor

(the kind used in a PC). In addition to the usual arithmetic and logic elements of a

general purpose microprocessor, the microcontroller typically integrates additional

elements such as read-write memory for data storage, read-only memory, such as

flash for code storage, EEPROM for permanent data storage, peripheral devices, and

input/output interfaces.

Digital electronics are electronics systems that use digital signals. Digital electronics

are representations of Boolean algebra and are used in computers, mobile phones, and

other consumer products. Digital electronics or any digital circuit are usually made

from large assemblies of logic gates, simple electronic representations of Boolean

logic functions.

Advantages:


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* Digital systems interface well with computers and are easy to control with

software. New features can often be added to a digital system without changing

hardware.

* Information storage can be easier in digital systems than in analog ones. The

noise-immunity of digital systems permit data to be stored and retrieved without

degradation. In an analog system, noise from aging and wear degrade the information

stored. In a digital system, as long as the total noise is below a certain level, theinformation can be recovered perfectly.

* Robustness: Digital electronics are robust because if the noise is less than the

noise margin then the system performs as if there were no noise at all. Therefore,

digital signals can be regenerated to achieve lossless data transmission, within certain

limits. Analog signal transmission and processing, by contrast, always introduces

noise.

Disadvantages:

* In some cases, digital circuits use more energy than analog circuits to accomplish

the same tasks, thus producing more heat as well. In portable or battery-powered

systems this can limit use of digital systems.

* Digital circuits are sometimes more expensive, especially in small quantities.

* The sensed world is analog, and signals from this world are analog quantities.Most useful digital systems must translate from continuous analog signals to discrete

digital signals. This causes quantization errors.

* Fragility-Digital systems can be fragile, in that if a single piece of digital data is

lost or misinterpreted, the meaning of large blocks of related data can completely

change. Digital fragility can be reduced by designing a digital system for robustness.

For example, a parity bit or other error management method can be inserted into the

signal path.

Multiplexing: Transmitting multiple signals over a single communications line or

computer channel. The two common multiplexing techniques are FDM, which

separates signals by modulating the data onto different carrier frequencies, and TDM,

which separates signals by interleaving bits one after the other.

Logic gate performs a logical operation on one or more logic inputs and produces a

single logic output. Because the output is also a logic-level value, an output of one

logic gate can connect to the input of one or more other logic gates. The logic

normally performed is Boolean logic and is most commonly found in digital circuits.

Logic gates are primarily implemented electronically using diodes or transistors.

Fanout is a measure of the ability of a logic gate output, implemented electronically,

to drive a number of inputs of other logic gates of the same type. In most designs,

logic gates are connected together to form more complex circuits, and it is common

for one logic gate output to be connected to several logic gate inputs. The technologyused to implement logic gates usually allows gate inputs to be wired directly together

with no additional interfacing circuitry required.

AND Gate: A HIGH output (1) results only if both the inputs to the AND gate are

HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output

results.

Equation:- C = A . B


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AND Symbol

AND Gate Constructed Using Only NAND Gates

OR Gate: A HIGH output (1) results if one or both the inputs to the gate are HIGH

(1). If neither input is HIGH, a LOW output (0) results.

'Military' OR Symbol

OR Gate Constructed Using Only NAND Gates

NOT Gate: A HIGH output (1) results if the inputs is LOW (0). If the input is HIGH

(1), a LOW output (0) results.

'Military' NOT symbol

NAND operation: is a logical operation on two logical values, that produces a value

of false if and only if both of its operands are true. In other words, it produces a value

of true if and only if at least one of its operands is false. It is one of the two solesufficient operators or functionally complete binary operators which can be used to

express all of the boolean functions of propositional logic. This property makes the

NAND gate crucial to modern digital electronics, including its use in NAND flash

memory and computer processor design. One way of expressing p NAND q is as

.

NOR Gate: A HIGH output (1) results if both the inputs to the gate are LOW (0). If

one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the

negation of the OR operator, thus forming a complete operation the combination of

which can be combined to generate any other logical function. By contrast, the OR

operator is monotonic as it can only change LOW to HIGH but not vice versa.

XOR Gate: A HIGH output (1) results if one, and only one, of the inputs to the gate

is HIGH (1). If both inputs are LOW (0) or both are HIGH (1), a LOW output (0)

results. This function is addition modulo 2. As a result, XOR gates are used to

implement binary addition in computers. A half adder consists of an XOR gate and an

AND gate.


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'Military' XOR Symbol

XOR gate constructed using only NAND gates

The XOR operation is a binary operation and is therefore defined only for two inputs.

It is nevertheless common in electronic design to talk of "XORing" three or more

signals. The most common interpretation of this usage is that the first two signals are

fed into an XOR gate, then the output of that gate is fed into a second XOR gate

together with the third signal, and so on for any remaining signals. The result is a

circuit that outputs a 1 when the number of 1s at its inputs is odd, and a 0 when the

number of incoming 1s is even. This makes it practically useful as a parity generator.

Adder: an adder or summer is a digital circuit that performs addition of numbers.

A half adderhas two inputs, generally labelled A and B, and two outputs, the sum S

and carry C. S is the two-bit XOR of A and B, and C is the AND of A and B.

Essentially the output of a half adder is the sum of two one-bit numbers, with C being

the most significant of these two outputs.

Half adder circuit diagram

The full adder takes into account a carry input such that multiple adders can be used

to add larger numbers. To remove ambiguity between the input and output carry lines,

the carry in is labelled Ci or Cin while the carry out is labelled Co or Cout.

Full adder circuit diagram

A full adder can be constructed from two half adders by connecting A and B to the

input of one half adder, connecting the sum from that to an input to the second adder,

connecting Ci to the other input and OR the two carry outputs

When multiple full adders are used with the carry ins and carry outs chained together

then this is called a ripple carry adder because the correct value of the carry bit

ripples from one bit to the next. It is possible to create a logical circuit using several


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full adders to add multiple-bit numbers. Each full adder inputs a Cin, which is the

Cout of the previous adder. This kind of adder is a ripple carry adder, since each carry

bit "ripples" to the next full adder.

FLIP FLOP :is a kind of bistable multivibrator, an electronic circuit which has two

stable states and thereby is capable of serving as one bit of memory. Today, the term

flip-flop has come to generally denote non-transparent (clocked or edge-triggered)

devices, while the simpler transparent ones are often referred to as latches. A flip-flop

is controlled by (usually) one or two control signals and/or a gate or clock signal. The

output often includes the complement as well as the normal output.A latch is transparent (not clocked) so that the input goes to output

immediately whereas a FF is non transparent (clocked).

Clocked devices are specially designed for synchronous (time-discrete)

systems and therefore one such device ignores its inputs except at the transition of a

dedicated clock signal (known as clocking, pulsing, or strobing). This causes the flip-

flop to either change or retain its output signal based upon the values of the input

signals at the transition. Some flip-flops change output on the rising edge of the clock,

others on the falling edge. the SR ("set-reset"), D ("delay"), T ("toggle"), and JK types

are the common ones

SR: Normally, in storage mode, the S and R inputs are both low, and feedback

maintains the Q and Q outputs in a constant state, with Q the complement of Q. If S

(Set) is pulsed high while R is held low, then the Q output is forced high, and stayshigh when S returns low; similarly, if R (Reset) is pulsed high while S is held low,

then the Q output is forced low, and stays low when R returns low

A gated SR latch circuit diagram constructed from NAND gates.

The R = S = 1 combination is called a restricted combination because, as both NOR

gates then output zeros, it breaks the logical equation Q = not Q.

With E high (enable true), the signals can pass through the input gates to the

encapsulated latch; all signal combinations except for (0,0) = hold then immediately

reproduce on the (Q,Q) output, i.e. the latch is transparent.With E low (enable false)

the latch is closed and remains in the state it was left the last time E was high..

SR latch operation

S R Action

0 0 Keep state

0 1 Q = 0

1 0 Q = 1

1 1 Restricted combination


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JK: The JK flip-flop augments the behavior of the SR flip-flop by interpreting the S =

R = 1 condition as a "flip" or toggle command To synthesize a D flip-flop, simply set

K equal to the complement of J. The JK flip-flop is therefore a universal flip-flop,

because it can be configured to work as an SR flip-flop, a D flip-flop or a T flip-flop.

T flip-flops: If the T input is high, the T flip-flop changes state ("toggles") whenever

the clock input is strobed. If the T input is low, the flip-flop holds the previous value

T Q Qnext Comment

0 0 0 hold state(no clk)

0 1 1 hold state(no clk)

1 0 1 toggle

1 1 0 toggle

D: The Q output always takes on the state of the D input at the moment of a rising

clock edge, and never at any other time. It is called the D flip-flop for this reason,

since the output takes the value of the D input or Data input, and Delays it by one

clock count. The D flip-flop can be interpreted as a primitive memory cell, zero-order

hold, or delay line.

Clock D Q Qprev

Rising edge 0 0 XRising edge 1 1 X

Non-Rising X constant

('X' denotes a Don't care condition, meaning the signal is irrelevant)

Race condition or race hazard is a flaw in a system or process whereby the output

and/or result of the process is unexpectedly and critically dependent on the sequence

or timing of other events. The term originates with the idea of two signals racing each

other to influence the output first. Avoided using master slave flip flops or using edge

triggered circuits.

Master Slave Flip Flop: consists of two JK flip flop connected in series. The clocks

to the two are mutually inverted and the feedback of output that comes back to theinput comes from the output of the second FF to the input of first

What is the principle of a microwave oven?A microwave oven works by passing non-ionizing microwave radiation, usually at a

frequency of 2.45 GHz, through the food. Microwave radiation is between common

radio and infrared frequencies. Water, fat, and other substances in the food absorb

energy from the microwaves in a process called dielectric heating. Many molecules

(such as those of water) are electric dipoles, meaning that they have a positive charge

JK Flip-Flop truth table

JK Qnext Comment

0 0 Qprev No change

0 1 0 Reset

1 0 1 Set

1 1 Qprev Toggle


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at one end and a negative charge at the other, and therefore rotate as they try to align

themselves with the alternating electric field of the microwaves. This molecular

movement creates heat as the rotating molecules hit other molecules and put them into

motion. Microwave heating is most efficient on liquid water, and much less so on fats

and sugars (which have less molecular dipole moment), and frozen water (where the

molecules are not free to rotate). The frequencies used in microwave ovens were

chosen based on two constraints. The first is that that they should be in one of the ISMbands set aside for non-communication purposes. Three additional ISM bands exist in

the microwave frequencies, but are not used for microwave cooking. Two of them are

centered on 5.8 GHz and 24.125 GHz, but are not used for microwave cooking

because of the very high cost of power generation at these frequencies. The third,

centered on 433.92 MHz, is a narrow band that would require expensive equipment to

generate sufficient power without creating interference outside the band, and is only

available in some countries. For household purposes, 2.45 GHz has the advantage

over 915 MHz in that 915 MHz is not an ISM band in all countries while 2.45 GHz is

available worldwide.

Most microwave ovens allow the user to choose between several power levels.

In most ovens, however, there is no change in the intensity of the microwave

radiation; instead, the magnetron is turned on and off in cycles of several seconds at atime.

Solenoid refers to a loop of wire, often wrapped around a metallic core, which

produces a magnetic field when an electrical current is passed through it. Solenoids

are important because they can create controlled magnetic fields and can be used as

electromagnets.

Magnetic field created by a solenoid

What is the difference between conductors and insulators?Current is the rate of flow of charges. More free electron means more current in

conductor. Conductor means element that allows electrons to follow through them

easily. Insulator means element that does not allow electrons to flow at all. Conductor

like copper atom; has free electrons that flow easily within the conductor. On the

other hand insulators like rubber; does not have any free elctrons. That's why

insulators are poor conductor of electricity. Dielectrics are also insulators but they

have a dipole structure, because of which they do not conduct electricity but when

placed in an electric field, the molecules orient themselves accordingly so as to allow

conduction of electric field.

Interrupt is an asynchronous signal from hardware indicating the need for attention

or a synchronous event in software indicating the need for a change in execution. A

hardware interrupt causes the processor to save its state of execution via a context

switch, and begin execution of an interrupt handler. Software interrupts are usually

implemented as instructions in the instruction set, which cause a context switch to an

interrupt handler similar to a hardware interrupt. Interrupts are a commonly used

technique for computer multitasking, especially in real-time computing


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An act of interrupting is referred to as an interrupt request ("IRQ").

* A maskable interrupt (IRQ) is a hardware interrupt that may be ignored by setting

a bit in an interrupt mask register's (IMR) bit-mask.

* Likewise, a non-maskable interrupt (NMI) is a hardware interrupt that does not

have a bit-mask associated with it - meaning that it can never be ignored

Before an interrupt is responded to:* The Program Counter (PC) is saved in a known place.

* All instructions before the one pointed to by the PC have fully executed.

* No instruction beyond the one pointed to by the PC has been executed (That is no

prohibition on instruction beyond that in PC, it is just that any changes they make to

registers or memory must be undone before the interrupt happens).

Read-only memory (ROM) is a class of storage media used in computers and other

electronic devices. Data stored in ROM cannot be modified. Modern types such as

EPROM and flash EEPROM can be erased and re-programmed multiple times; they

are still described as "read-only memory" because the reprogramming process is

generally infrequent, comparatively slow, and often does not permit random access

writes to individual memory locations, which are possible when reading a ROM.

Programmable read-only memory (PROM), or one-time programmable ROM

(OTP), can be written to or programmed via a special device called a PROM

programmer. Typically, this device uses high voltages to permanently destroy or

create internal links (fuses or antifuses) within the chip. Consequently, a PROM can

only be programmed once.

Erasable programmable read-only memory (EPROM) can be erased by exposure

to strong ultraviolet light (typically for 10 minutes or longer), then rewritten with a

process that again requires application of higher than usual voltage. Repeated

exposure to UV light will eventually wear out an EPROM, but the endurance of most

EPROM chips exceeds 1000 cycles of erasing and reprogramming. EPROM chip

packages can often be identified by the prominent quartz "window" which allows UV

light to enter. After programming, the window is typically covered with a label to

prevent accidental erasure.

Electrically erasable programmable read-only memory (EEPROM) is based on a

similar semiconductor structure to EPROM, but allows its entire contents (or selected

banks) to be electrically erased, then rewritten electrically, so that they need not be

removed from the computer (or camera, MP3 player, etc.). Writing or flashing an

EEPROM is much slower (milliseconds per bit) than reading from a ROM or writing

to a RAM (nanoseconds in both cases).

Random access memory (RAM) is a type of computer data storage. Today it takes

the form of integrated circuits that allow the stored data to be accessed in any order,

i.e. at random. The word random thus refers to the fact that any piece of data can be

returned in a constant time, regardless of its physical location and whether or not it is

related to the previous piece of data.

Flash memory is non-volatile computer memory that can be electrically erased and

reprogrammed. It is a technology that is primarily used in memory cards and USB


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flash drives for general storage and transfer of data between computers and other

digital products. It is a specific type of EEPROM that is erased and programmed in

large blocks; in early flash the entire chip had to be erased at once. Flash memory

costs far less than byte-programmable EEPROM and therefore has become the

dominant technology wherever a significant amount of non-volatile, solid-state

storage is needed. Flash memory is non-volatile, which means that it does not need

power to maintain the information stored in the chip. In addition, flash memory offersfast read access times and better kinetic shock resistance than hard disks. Another

feature of flash memory is that when packaged in a "memory card", it is enormously

durable, being able to withstand intense pressure, extremes of temperature, and

immersion in water.

What is the difference between ic and pcb?

An integrated circuit (IC) is an electronic circuit miniaturized to fit on a small piece of

semiconductor material such as silicon. This piece of silicon is encased inside a

hermetically sealed plastic, metal, or ceramic package that prevents it being damaged

from dust, moisture, and contact with other objects. The package also serves to allow

easier connections to aprinted circuit board(PCB). The chip inside the IC package is

so small that connecting it directly to a PCB would be difficult.The purpose of a PCB is to connect ICs and discreet components together to

form larger operational curcuits. PCBs may also allow parts to be mounted to them

such as card sockets. They are sometimes used as heat sinks for components that

generate heat. This is done by making a large copper area then mating the component

to the PCB so that it touches the copper area and transfers heat to it.

Before PCBs, components were connected together with wires, in a scheme

called "point-to-point" wiring. It was messy and unreliable when compared to PCBs.

Multivibrator is an electronic circuit used to implement a variety of simple two-state

systems such as oscillators, timers and flip-flops. The most common form is the

astable or oscillating type, which generates a square wave - the high level of

harmonics in its output is what gives the multivibrator its common name.There are

three types of multivibrator circuit:

* astable, in which the circuit is not stable in either state - it continuously oscillates

from one state to the other.

* monostable, in which one of the states is stable, but the other is not - the circuit

will flip into the unstable state for a determined period, but will eventually return to

the stable state. Such a circuit is useful for creating a timing period of fixed duration

in response to some external event. This circuit is also known as a one shot. A

common application is in eliminating switch bounce.

* bistable, in which the circuit will remain in either state indefinitely. The circuit

can be flipped from one state to the other by an external event or trigger. Such a

circuit is important as the fundamental building block of a register or memory device.This circuit is also known as a flip-flop.

Nuclear fusion is the process by which multiple atomic particles join together to form

a heavier nucleus. It is accompanied by the release or absorption of energy. Nuclear

fusion occurs naturally in stars. It takes considerable energy to force nuclei to fuse,

even those of the lightest element, hydrogen. This is because all nuclei have a positive

charge (due to their protons), and as like charges repel, nuclei strongly resist being put

too close together. Accelerated to high speeds (that is, heated to thermonuclear


22/40

temperatures), however, they can overcome this electromagnetic repulsion and get

close enough for the attractive nuclear force to be stronger, achieving fusion. The

fusion of lighter nuclei, creating a heavier nucleus and a free neutron, will generally

release more energy than it took to force them together-an exothermic process that

can produce self-sustaining reactions.

Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei)often producing free neutrons and other smaller nuclei, which may eventually produce

photons (in the form of gamma rays). Fission of heavy elements is an exothermic

reaction which can release large amounts of energy both as electromagnetic radiation

and as kinetic energy of the fragments (heating the bulk material where fission takes

place). Fission is a form of elemental transmutation because the resulting fragments

are not the same element as the original atom. The products of nuclear fission are

radioactive and remain so for significant amounts of time, giving rise to a nuclear

waste problem.

Active versus passive devices

An active device is any type of circuit component with the ability to electrically

control electron flow (electricity controlling electricity). In order for a circuit to beproperly called electronic, it must contain at least one active device. Components

incapable of controlling current by means of another electrical signal are called

passive devices. Resistors, capacitors, inductors, transformers, and even diodes are all

considered passive devices. Active devices include, but are not limited to, vacuum

tubes, transistors, silicon-controlled rectifiers (SCRs), and TRIACs.

All active devices control the flow of electrons through them. Some active

devices allow a voltage to control this current while other active devices allow

another current to do the job. Devices utilizing a static voltage as the controlling

signal are called voltage-controlled devices. Devices working on the principle of one

current controlling another current are known as current-controlled devices. Vacuum

tubes are voltage-controlled devices while transistors are made as either voltage-

controlled or current controlled types. The first type of transistor successfully

demonstrated was a current-controlled device.

Operational amplifier(741)

An operational amplifier, often called an op-amp , is a DC-coupled high-gain

electronic voltage amplifier with differential inputs and, usually, a single output.

Typically the output of the op-amp is controlled either by negative feedback, which

largely determines the magnitude of its output voltage gain, or by positive feedback,

which facilitates regenerative gain and oscillation. High input impedance at the input

terminals and low output impedance are important typical characteristics. The


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amplifier's differential inputs consist of an inverting input and a non-inverting input,

and ideally the op-amp amplifies only the difference in voltage between the two. This

is called the "differential input voltage". In its most common use, the op-amp's output

voltage is controlled by feeding a fraction of the output signal back to the inverting

input. This is known as negative feedback. If that fraction is zero, i.e., there is no

negative feedback, the amplifier is said to be running "open loop" and its output is the

differential input voltage multiplied by the total gain of the amplifier. Because themagnitude of the open-loop gain is typically very large and not well controlled by the

manufacturing process, op-amps are not usually used without negative feedback.

Unless the differential input voltage is extremely small, open-loop operation results in

op-amp saturation.

For any input voltages the ideal op-amp has

* infinite open-loop gain,

* infinite bandwidth,

* infinite input impedances (resulting in zero input currents),

* zero offset voltage,

* infinite slew rate,

* zero output impedance, and

* zero noise.Imperfections

* Saturation output voltage is limited to a minimum and maximum value close

to the power supply voltages.

* Slewing the amplifier's output voltage reaches its maximum rate of change.

Measured as the slew rate, it is usually specified in volts per microsecond. Slewing is

usually caused by internal capacitances in the amplifier, especially those used to

implement its frequency compensation.

* Non-linear transfer function The output voltage may not be accurately

proportional to the difference between the input voltages. It is commonly called

distortion when the input signal is a waveform. This effect will be very small in a

practical circuit if substantial negative feedback is used.

DC imperfections

* Finite gain the effect is most pronounced when the overall design attempts to

achieve gain close to the inherent gain of the op-amp.

* Finite input resistance this puts an upper bound on the resistances in the

feedback circuit.

* Nonzero output resistance

* Input bias current a small amount of current (typically ~10 nA for bipolar op-

amps, or picoamperes for CMOS designs) flows into the inputs. This current is

mismatched slightly between the inverting and non-inverting inputs

* Input offset voltage the voltage required across the op-amp's input terminals to

drive the output voltage to zero. In the perfect amplifier, there would be no input

offset voltage.AC imperfections

* Finite bandwidth

* Input capacitance most important for high frequency operation because it

further reduces the open loop bandwidth of the amplifier.

Linear circuit applicationsDifferential amplifier:


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The circuit shown is used for finding the difference of two voltages each multiplied

by some constant (determined by the resistors).

Inverting amplifier

Inverts and amplifies a voltage (multiplies by a negative constant)

Zin =Rin (because V is a virtual ground)Non-inverting amplifier

Amplifies a voltage (multiplies by a constant greater than 1)

Summing amplifier

Sums several (weighted) voltages


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When , andRfindependent

When Output is inverted Input impedanceZn =Rn, for each input (V is a virtual ground)

Integrator

Integrates the (inverted) signal over time

(where Vin and Vout are functions of time, Vinitial is the output voltage of the integrator

at time t= 0.)

Note that this can also be viewed as a type of electronic filter.Differentiator

(where Vin and Vout are functions of time)

Note that this can also be viewed as a type of electronic filter.Comparator

Compares two voltages and outputs one of two states depending on which is greater

Skin effect is the tendency of an alternating electric current (AC) to distribute itself

within a conductor so that the current density near the surface of the conductor is

greater than that at its core. That is, the electric current tends to flow at the "skin" of

the conductor. The skin effect causes the effective resistance of the conductor to

increase with the frequency of the current. current densityJin an infinitely thickplane

conductor decreases exponentially with depth from the surface, as follows:

where d is a constant called the skin depth.


26/40

Faraday's law of induction:The induced electromotive force in a closed loop of wire is directly

proportional to the time rate of change of magnetic flux through the loop.

(A changing magnetic field can create an electric field)

Moving a permanent magnet near a conductor (such as a metal wire) produces a

voltage in that conductor. The resulting voltage is proportional to the speed ofmovement: moving the magnet twice as fast produces twice the voltage.

For a tightly-wound coil of wire, composed of N loops with the same area, Faraday's

law states that:

where

is the electromotive force (emf)

B is the magnetic flux

The direction of the electromotive force (the negative sign in the above formula) was

first given by Lenz's law.

Lenz's law states that the induced current in a loop is in the direction that creates a

magnetic field that opposes the change in magnetic flux through the area enclosed by

the loop. That is, the induced current tends to keep the original magnetic flux through

the field from changing.

Convert AC to DC:Half Wave Rectifier:

Full-wave rectification

Full-wave rectification converts both polarities of the input waveform to DC(direct

current), and is more efficient. However, in a circuit with a non-center tapped

transformer, four diodes are required instead of the one needed for half-wave

rectification. Four rectifiers arranged this way are called a diode bridge or bridge

rectifier:

A full-wave rectifier converts the whole of the input waveform to one of constant

polarity (positive or negative) at its output by reversing the negative (or positive)

portions of the alternating current waveform. The positive (or negative) portions thus

combine with the reversed negative (or positive) portions to produce an entirely

positive (or negative) voltage/current waveform.


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For single-phase AC, if the transformer is center-tapped, then two diodes back-to-

back (i.e. anodes-to-anode or cathode-to-cathode) form a full-wave rectifier (in this

case, the voltage is half of that for the non-tapped bridge circuit above, and the

diagram voltages are not to scale).

Rectifier output smoothing: While half- and full-wave rectification suffice to deliver a

form of DC output, neither produces constant-voltage DC. In order to produce steady

DC from a rectified AC supply, a smoothing circuit, sometimes called a filter, is

required. In its simplest form this can be what is known as a Filter capacitor placed at

the DC output of the rectifier. There will still remain an amount of AC ripple voltage

where the voltage is not completely smoothed. To further reduce this ripple, a

capacitor-input filter can be used. This complements the reservoir capacitor with a

choke and a second filter capacitor, so that a steadier DC output can be obtained

across the terminals of the filter capacitor. The choke presents a high impedance to

the ripple current

Superconductivity is a phenomenon occurring in certain materials at extremely low

temperatures, characterized by exactly zero electrical resistance and the exclusion of

the interior magnetic field. The electrical resistivity of a metallic conductor decreases

gradually as the temperature is lowered. However, in ordinary conductors such as

copper and silver, impurities and other defects impose a lower limit. Even near

absolute zero a real sample of copper shows a non-zero resistance. The resistance of a

superconductor, on the other hand, drops abruptly to zero when the material is cooled

below its "critical temperature". An electric current flowing in a loop ofsuperconducting wire can persist indefinitely with no power source.

Transponder: An automatic device that receives, amplifies, and retransmits a signal

on a different frequency (see also broadcast translator).

Shift register is a group of flip flops set up in a linear fashion which have their inputs

and outputs connected together in such a way that the data are shifted down the line

when the circuit is activated. Shift registers can have a combination of serial and

parallel inputs and outputs, including serial-in, parallel-out (SIPO) and parallel-in,

serial-out (PISO) types. There are also types that have both serial and parallel input

and types with serial and parallel output. There are also bi-directional shift registers

which allow you to vary the direction of the shift register. The serial input and outputsof a register can also be connected together to create a circular shift register.


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4-Bit SIPO Shift Register

Counter is a device which stores (and sometimes displays) the number of times a

particular event or process has occurred, often in relationship to a clock signal.

Asynchronous (ripple) counters Synchronous counters Johnson counters Decade counters Up-Down counters Ring counters

Asynchronous counters, also known as ripple counters, are not clocked by a common

pulse and hence every flip-flop in the counter changes at different times. The flip-

flops in an asynchronous counter is usually clocked by the output pulse of the

preceding flip-flop. The first flip-flop is clocked by an external event. A synchronous

counter however, has an internal clock, and the external event is used to produce a

pulse which is synchronised with this internal clock.

Asynchronous (ripple) counters

Asynchronous Counter created from JK flip-flops.(J,K Set High)

The simplest counter circuit is a single D-type flip flop, with its D (data) input fed

from its own inverted output. This circuit can store one bit, and hence can count from

zero to one before it overflows (starts over from 0). This counter will increment once

for every clock cycle and takes two clock cycles to overflow, so every cycle it will

alternate between a transition from 0 to 1 and a transition from 1 to 0. Notice that this

creates a new clock with a 50% duty cycle at exactly half the frequency of the inputclock. If this output is then used as the clock signal for a similarly arranged D flip flop

(remembering to invert the output to the input), you will get another 1 bit counter that

counts half as fast. Putting them together yields a two bit counter:

cycle Q1 Q0 (Q1:Q0)decimal

0 0 0 0

1 0 1 1

2 1 0 2

3 1 1 3

4 0 0 0

You can continue to add additional flip flops, always inverting the output to its owninput, and using the output from the previous flip flop as the clock signal. The result is

called a ripple counter, which can count to 2n-1 where n is the number of bits (flip

flop stages) in the counter. Ripple counters suffer from unstable outputs as the

overflows "ripple" from stage to stage, but they do find frequent application as

dividers for clock signals, where the instantaneous count is unimportant

NOTE: Replace D by simple T flip flop to create simple ripple counter


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Synchronous counters

Where a stable count value is important across several bits, which is the case in most

counter systems, synchronous counters are used. These also use flip-flops, either the

D-type or the more complex J-K type, but here, each stage is clocked simultaneously

by a common clock signal. Logic gates between each stage of the circuit control data

flow from stage to stage so that the desired count behaviour is realised. Synchronous

counters can be designed to count up or down, or both according to a direction input,

and may be pre-settable via a set of parallel "jam" inputs. Most types of hardware-

based counter are of this type.A simple way of implementing the logic for each bit of an ascending counter

(which is what is shown in the image to the right) is for each bit to toggle when all of

the less significant bits are at a logic high state. For example, bit 1 toggles when bit 0

is logic high; bit 2 toggles when both bit 1 and bit 0 are logic high; bit 3 toggles when

bit 2, bit 1 and bit 0 are all high; and so on.

4-bit Synchronous Binary Up-Counter

MOD-N/Divide-by-N Counters

Normal binary counter counts from 0 to 2N - 1, where N is the number od bits/flip-

flops in the counter. In some cases, we want it to count to numbers other than 2N - 1.

This can be done by allowing the counter to skip states that are normally part of the

counting sequence. There are a few methods of doing this. One of the most common

methods is to use the CLEAR input on the flip-flops using asynchronous clear when

the o/p reaches the desired no.

Binary Coded Decimal (BCD) Counters

The BCD counter is just a special case of the MOD-N counter (N = 10). BCD

counters are very commonly used because most human beings count in decimal.

Ring Counters

Ring counters are implemented using shift registers. It is essentially a circulating shift

register connected so that the last flip-flop shifts its value into the first flip-flop. There


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is usually only a single 1 circulating in the register, as long as clock pulses are

applied.

4-bit Synchronous Ring Counter

In the diagram above, assuming a starting state of Q3 = 1 and Q2 = Q1 = Q0 = 0. At

the first pulse, the 1 shifts from Q3 to Q2 and the counter is in the 0100 state. The

next pulse produces the 0010 state and the third, 0001. At the fourth pulse, the 1 at Q0

is transferred back to Q3, resulting in the 1000 state, which is the initial state.

Subsequent pulses will cause the sequence to repeat, hence the name ring counter.

The ring counter above functions as a MOD-4 counter since it has four distinct statesand each flip-flop output waveform has a frequency equal to one-fourth of the clock

frequency. A ring counter can be constructed for any MOD number. A MOD-N ring

counter will require N flip-flops connected in the arrangement as the diagram above.

Johnson/Twisted-Ring Counters

The Johnson counter, also known as the twisted-ring counter, is exactly the same as

the ring counter except that the inverted output of the last flip-flop is connected to the

input of the first flip-flop. The Johnson counter works in the following way : Take the

initial state of the counter to be 000. On the first clock pulse, the inverse of the last

flip-flop will be fed into the first flip-flop, producing the state 100. On the second

clock pulse, since the last flip-flop is still at level 0, another 1 will be fed into the first

flip-flop, giving the state 110. On the third clock pulse, the state 111 is produced. On

the fourth clock pulse, the inverse of the last flip-flop, now a 0, will be shifted to thefirst flip-flop, giving the state 011. On the fifth and sixth clock pulse, using the same

reasoning, we will get the states 001 and 000, which is the initial state again. Hence,

this Johnson counter has six distinct states : 000, 100, 110, 111, 011 and 001, and the

sequence is repeated so long as there is input pulse. Thus this is a MOD-6 Johnsoncounter. The MOD number of a Johnson counter is twice the number of flip-flops.

multiplexer or mux (occasionally the term muldex is also found, for a combination

multiplexer-demultiplexer) is a device that performs multiplexing; it selects one of

many analog or digital input signals and outputs that into a single line.

Demultiplexers take one data input and a number of selection inputs, and they have

several outputs. They forward the data input to one of the outputs depending on thevalues of the selection inputs. Demultiplexers are sometimes convenient for designing

general purpose logic, because if the demultiplexer's input is always true, the

demultiplexer acts as a decoder.

Encoder is a device used to change a signal (such as a bitstream) or data into a code.

A single bit 4 to 2 encoder takes in 4 bits and outputs 2 bits. It is assumed that there

are only 4 types of input signals: 0001, 0010, 0100, 1000.

I3 I2 I1 I0 O1 O0


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0 0 0 1 0 0

0 0 1 0 0 1

0 1 0 0 1 0

1 0 0 0 1 1

A priority encoder prioritizes more significant bits in the data stream, and once it

finds a high signal will ignore all other bits.

Decoder is a device which does the reverse of an encoder, undoing the encoding so

that the original information can be retrieved. The same method used to encode is

usually just reversed in order to decode.

Pull-up resistors are resistors used in the design of electronic logic circuits to ensure

that inputs to logic systems settle at expected logic levels if external devices are

disconnected. Pull-up resistors may also be used at the interface between two different

types of logic devices, possibly operating at different power supply voltages.

The idea of a pullup resistor is that it weakly "pulls" the voltage of the wire it's

connected to towards 5V (or whatever voltage represents a logic "high"). However,

the resistor is intentionally weak (high-resistance) enough that, if something else

strongly pulls the wire toward 0V, the wire will go to 0V.

BUS: In computer architecture, a bus is a subsystem that transfers data between

computer components inside a computer or between computers. Unlike a point-to-

point connection, a bus can logically connect several peripherals over the same set of

wires. Each bus defines its set of connectors to physically plug devices, cards or

cables together. Early computer buses were literally parallel electrical buses with

multiple connections, but the term is now used for any physical arrangement that

provides the same logical functionality as a parallel electrical bus.

Address bus is a computer bus, used by CPUs or DMA-capable units for

communicating the physical addresses of computer memory elements/locations that

the requesting unit wants to access (read/write). The width of an address bus, along

with the size of addressable memory elements, determines how much memory can be

accessed. For example, a 16-bit wide address bus (commonly used in the 8-bit

processors of the 1970s and early 1980s) reaches across 216

= 65,536 = 64 K memory

locations, whereas a 32-bit address bus (common in PC processors as of 2004) can

address 232 = 4,294,967,296 = 4 G locations.

In most microcomputers such addressable "locations" are 8-bit bytes. In such

case the above examples translate to 64 kibibytes (KiB) and 4 gibibytes (GiB)

respectively. Historically, there were also some examples of computers, which were

able to address only areas of a larger size (words), such as 16, 32, 36 bits long.

Control bus is (part of) a computer bus, used by CPUs for communicating with otherdevices within the computer. While the address bus carries the information on which

device the CPU is communicating with and the data bus carries the actual data being

processed, the control bus carries commands from the CPU and returns status signals

from the devices, for example if the data is being read or written to the device the

appropriate line (read or write) will be active (logic zero).

Assembly language is a low-level language for programming computers. It

implements a symbolic representation of the numeric machine codes and other


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constants needed to program a particular CPU architecture. This representation is

usually defined by the hardware manufacturer, and is based on abbreviations (called

mnemonics) that help the programmer remember individual instructions, registers,

etc. An assembly language is thus specific to a certain physical or virtual computer

architecture (as opposed to most high-level languages, which are portable).

A utility program called an assembler is used to translate assembly languagestatements into the target computer's machine code. The assembler performs a more

or less isomorphic translation (a one-to-one mapping) from mnemonic statements into

machine instructions and data. (This is in contrast with high-level languages, in which

a single statement generally results in many machine instructions. A compiler,

analogous to an assembler, is used to translate high-level language statements into

machine code; or an interpreter executes statements directly.)

A high-level programming language is a programming language that, in comparison

to low-level programming languages, may be more abstract, easier to use, or more

portable across platforms. Such l

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