Archive for the ‘Training & Project Guidance’ Category

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Thursday, December 4th, 2014

• Applications developer
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How to Improve English

Thursday, December 4th, 2014
The importance of the English language cannot be overemphasized. Comfort with English is almost a prerequisite for success in the world today. Regardless of the industry, proficiency in English is an important factor in both hiring and promotion decisions.

A lot of us have studied English in school and are fairly comfortable with reading and writing. However, we hesitate while speaking because we feel that we lack the fluency and may make grammatical mistakes. We are afraid of speaking English in formal situations and we are quick to switch to our native language once we are in the company of our family and friends.

There is no quick fix when it comes to improving your command over a particular language. It always requires a lot of time and effort.

Here are EnglishLeap’s top ten tips for success in achieving proficiency and fluency in English:

  1. Do not hesitate. Talk to whoever you can. Decide among your circle of friends that you will only talk in English with each other. This way you can get rid of hesitation and also have your friends correct you when you are wrong.

  2. Start a conversation with strangers in English. Since you do not know them personally, you will feel less conscious about what they would feel about you.

  3. Maintaining a diary to record the events of your day is a great way topractice your writing skills. Take your time to use new words and phrases when you write in your diary.

  4. Read the newspaper. Read it aloud when you can. Concentrate on each word. Note down the words you don’t understand and learn their meanings. Try to use these words in your own sentences.

  5. Watch English movies and English shows on television. Initially, you can read the sub-titles to follow the conversation. As you practice more, you will realize that you are able to follow the conversation without needing to read the sub-titles.

  6. Set aside an hour every day to watch English news channels. This is one of the most effective ways of improving your comprehension.

  7. Podcasts are available on the internet. These are audio and video files and many of these can be downloaded for free. These are a great way to practice listening skills and develop an understanding of different accents.

  8. It is usually quite difficult for a beginner to understand the words of an English song as there is background music and the accent of the artist may be unfamiliar to the listener. Read the lyrics while you listen to the song and you will comprehend better. Once you start following the voice of a particular singer, you will find it much easier to understand the singer’s other songs too.

  9. Another effective way is to record your own voice and listen to it. You will notice hesitations and pauses. You may also notice that you make some grammatical mistakes while speaking that you do not make while writing. You must aim to improve and rectify these mistakes in subsequent recordings.

  10. Ask people who speak better for advice. There is no shame in seeking help especially if you are trying to improve yourself. Talk to them in English and ask them to correct you whenever you are wrong.

Stepper Motor

Thursday, December 4th, 2014

stepper motor (or step motor) is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor’s position can then be commanded to move and hold at one of these steps without any feedback sensor (an open-loop controller), as long as the motor is carefully sized to the application.

Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.

Fundamentals of operation

DC brush motors rotate continuously when voltage is applied to their terminals. Stepper motors, on the other hand, effectively have multiple “toothed” electromagnets arranged around a central gear-shaped piece of iron. The electromagnets are energized by an external control circuit, such as a microcontroller. To make the motor shaft turn, first, one electromagnet is given power, which makes the gear’s teeth magnetically attracted to the electromagnet’s teeth. When the gear’s teeth are aligned to the first electromagnet, they are slightly offset from the next electromagnet. So when the next electromagnet is turned on and the first is turned off, the gear rotates slightly to align with the next one, and from there the process is repeated. Each of those slight rotations is called a “step”, with an integer number of steps making a full rotation. In that way, the motor can be turned by a precise angle.

Stepper motor characteristics

  • Stepper motors are constant power devices.
  • As motor speed increases, torque decreases. Most motors exhibit maximum torque when stationary; however, the torque of a motor when stationary (holding torque) defines the ability of the motor to maintain a desired position while under external load. The torque curve may be extended by using current limiting drivers and increasing the driving voltage (sometimes referred to as a ‘chopper’ circuit; there are several off the shelf driver chips capable of doing this in a simple manner).
  • Steppers exhibit more vibration than other motor types, as the discrete step tends to snap the rotor from one position to another (called a detent). The vibration makes stepper motors noisier than DC motors. This vibration can become very bad at some speeds and can cause the motor to lose torque or lose direction. This is because the rotor is being held in a magnetic field which behaves like a spring. On each step the rotor overshoots and bounces back and forth, “ringing” at its resonant frequency. If the stepping frequency matches the resonant frequency then the ringing increases and the motor loses synchronism, resulting in positional error or a change in direction. At worst there is a total loss of control and holding torque so the motor is easily overcome by the load and spins almost freely. The effect can be mitigated by accelerating quickly through the problem speeds range, physically damping (frictional damping) the system, or using a micro-stepping driver. Motors with a greater number of phases also exhibit smoother operation than those with fewer phases (this can also be achieved through the use of a micro-stepping driver).
  • Stepper motors with higher inductance coils provide greater torque at low speeds and lower torque at high speeds compared to stepper motors with lower inductance coils.

Open-loop versus closed-loop commutation

Steppers are generally commutated (electrically switched) using “open loop” electronics, i.e., the driver has no feedback on where the rotor actually is. Stepper motor systems must thus generally be oversized, especially if the load inertia is high, or there is widely varying load, so that there is no possibility that the motor will lose steps. This has often caused the system designer to consider the trade-offs between a closely sized but expensive servomechanism system and an oversized but relatively cheap stepper.

A new development in stepper control is to incorporate a rotor position feedback (e.g., a rotary encoder or resolver), so that the commutation can be made optimal for torque generation according to actual rotor position. This turns the stepper motor into a high pole count brushless servo motor, with exceptional low speed torque and position resolution. An advance on this technique is to normally run the motor in open loop mode, and only enter closed loop mode if the rotor position error becomes too large; this will allow the system to avoid hunting or oscillating, a problem when servo gain is set too high.


There are four main types of stepper motors:

  1. Permanent magnet stepper (can be subdivided in to ‘tin-can’ and ‘hybrid’, tin-can being a cheaper product, and hybrid with higher quality bearings, smaller step angle, higher power density)
  2. Hybrid synchronous stepper
  3. Variable reluctance stepper
  4. Lavet type stepping motor

Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the attraction or repulsion between the rotor PM and the stator electromagnets. Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle that minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the stator magnet poles. Hybrid stepper motors are named because they use a combination of PM and VR techniques to achieve maximum power in a small package size.

New domains of research in electronics

Thursday, December 4th, 2014

Nanometer Wavelength Printing

  • Electronic circuits are “printed” by exposing silicon wafers to ultraviolet light and etching the circuit design into the silicon surface. The complexity of the chips is limited by how small the wavelengths of the light are; in a real world analogy, you cannot draw a finer line then the thickness of your pen tip. There is research into using different combinations of lenses and electromagnetic spectrum emissions to etch at even smaller nanometer resolutions. However, there may be a limit to this process if the wires are printed too close to each other; the magnetic fields of the electrons themselves could interact with each other and slow each other down.

Liquid Cooling

  • Liquid cooling is well understood when it comes to mechanical applications — your car engine, for example — but cooling circuits with liquids is still being researched. In 2011, only high-end computers use liquid cooling and even then there is a risk of leaks and damage to the circuits. Research is being conducted into nonconductive coolants and leakproof heat exchanges. Laptop applications are also being researched as laptop computers grow in power to rival desktops.


  • Photonics is the science of using light, primarily lasers, to transmit information and data. Fiber-optic Internet connections are a example of this technology already being used in the real world. In the field of electronics there is a push to use photonics to replace circuits, with lasers taking the place of electrons and circuits being made of fiber-optic wires and mirrors. The benefit of this design is that there is very little heat and programming needs little adaption, since a photonics circuit can operate in binary the same as an electrical circuits.

Quantum Computing

  • The cutting edge of electronics engineering is quantum computing, which is incredibly complex but could allow for actual artificial intelligences. Quantum computing uses quantum particles instead of binary bits. The difference is that quantum particles can be used to run trinary programs. Quantum particles can have three polarities: up, down, and “maybe.” Until a quantum particle is observed, it can have either polarity depending on its entanglement with another quantum particle.

OCB Digital Switching System

Monday, September 24th, 2012


All new technology switching systems are based on Stored Program Controlconcept. The call processing programmes are distributed over different controlorgans of the system and are stored in ROM / RAM of different control units.Processor in the control units by using the programme and data stored inunit ROM / RAM process and handle calls. Handling or processing call means toultimately establish a connection in a switch between i/c and o/g ends. Dependingon the name and architecture of control units and switch may change but criterionfor switching remains more or less the same.



OCB-283 is digital switching system which supports a variety ofcommunication needs like basic telephony, ISDN, etc. This system has beendeveloped by CIT ALCATEL of France and therefore has many similarities to itspredecessor E-10B (also known as OCB-181 in France).

SILENT FEATURES OF THE SYSTEM:1. It is a digital switching with single ‘T’ stage switch. A maximum of 2048PCM’s can be connected.2. It supports both analog and digital subscribers.3. It supports all the existing signalling systems, like decadic, MF (R2), CASand also CCITT#7 signalling system.4. It provides telephony, ISDN, Data communication, cellular radio, and othervalue added services.5. The system has ‘automatic’ recovery feature. When a serious fault occurs ina control unit, it gives a message to SMM. The SMM puts this unit out of service,loads the software of this unit in a back up unit and brings it into service.Diagnostic programmes are run on the faulty unit and the diagnostics is printed ona terminal.6. It has a double remoting facility.Subscribers access unit can be placed at aremote place and connected to the main exchange through PCM links. Further,line concentrators can also be placed at a remote location and connected to theCSNL or CSND through PCMs.7. Various units of OCB 283 system are connected over token rings. Thisenables fast exchange of information and avoids complicated links and wiringbetween various units.8. The charge accounts of subscribers are automatically saved in the disc, oncein a day. This avoids loss of revenue in case of battery failure.9. The traffic handling capacity of the system is huge.10. The exchange can be managed either locally or from an NMC through 64kb/s link.11. All the control units are implemented on the same type of hardware. This iscalled a station.12. The system is made up of only 35 types of cards. This excludes the cardsrequired for CSN. Due to this, the number of spare cards to be kept formaintenance, are drastically reduced.13. The system has modular structure. The expansion can be very easily carriedout by adding necessary hardware and software.14. The SMMs are duplicated with one active other standby. In case of faults,switch over takes place automatically.15. The hard disc is very small in size,compact and maintenance free. It has avery huge memory capacity of 1.2 Giga bytes.16. The space requirement is very small.17. There is no fixed or rigid rack and suite configuration in the system.

SUBSCRIBERS FACILITY PROVIDED BY OCB-283OCB-283 provides a large number of subscriber facilities. Somefacilities are available to only digital subscribers and as such they cannot beavailed by analog subscribers. To avail these facilities subscriber number aregiven special categories by man machine commands.Facilities to analogue subscribers-• A line can be made only outgoing or incoming.• Immediate hot line facility-The subscriber is connected to another predetermined subscriber on lifting thehandset without dialling any number.• Delayed hot line facility-When subscriber lifts the handset, dial tone is provided he can dial any number. Ifhe does not dial a number, within a predetermined time, he is connected topredetermined number.• Abbreviated dialling-The subscriber can record a short code and its corresponding full number in thememory. Later he dial this number, he has to only dial short code.• Call forwarding-When activated, incoming calls to the subscriber gets transferred to the numbermentioned by the subscriber while activating the facility.• Conference between four subscribers-Two subscribers while in conversation can include two more subscribers bypressing button and dialling their numbers.• Call waiting indication-When a subscriber is engaged in conversation and if he gets an incoming call, anindication is given in the form of tone. Hearing this, the subscriber has option,either to hold the subscriber in conversation and attend the waiting call or todisconnect this subscriber and attend the waiting call. In the former case, he canrevert back to the earlier subscriber.• Automatic call back on busyIf this facility is activated and if the called subscriber is found busy, the callingsubscriber simply replaces the receiver. The system keeps watch on the calledsubscriber and when it becomes free, a ring is given to both the subscribers. Onlifting they can talk to each other.• Priority line-Calls from this line are processed and put through even when the number of freechannels are within a threshold.• Malicious call identification-In this category, the number of calling subscriber is printed on the terminal• Battery reversal- the system extends battery reversal when called subscriberanswers. • Detailed billing-The system provides detailed bills giving details of date, time, etc.• Absent subscriber service-When activated, the incoming calls are diverted to absent subscriber service forsuitable instructions or information.Facilities to digital subscribers:Digital subscribers are provided all the facilities available to analogsubscribers. In addition, they are provided following facilities which are calledISDN services. An ISDN subscriber can use many electronic devices on itstelephone line and can utilize them for two or more simultaneous calls of either• Voice• Data• VideoThe ISDN or Digital Subscribers of OCB-283 can be provided the following typesof connections• 2B+D LINE :- 2 Voice Channel of 64kbps and 1 Data Channel of 16kbps• 30 B+D LINE :- 30 Voice Channel of 64kbps and 1 Data Channel of 64kbps

The following is the list of some of the services to digital subscribers:1. It provides 64kb/s digital connectivity between two subscribers for datacommunication.2. The system provides facsimile services.3. It provides videotext services.4. It provides display of calling subscriber number on called subscribers telephone.5. It also provides the facility for restriction of the display of calling subscribernumber on the called subscriber’s terminal.6. Charging advice – The system is capable of providing charging advice either in realtime or at the end of the call.7. User to user signaling – The system permits transfer to mini messages betweencalling and called subscribers during call set up and ringing phase.8. Terminal portability during the call – A subscriber can unplug terminal, carry it tosome other place or room and resume the call within 3 minutes.

TIME SWITCH CONCEPT: The time switch comprises of a Speech Buffer Memory, A ControlMemory, An Incoming Highway Of Digital Speech In Parallel Bits and AnOutgoing Highway. This is an Input Associated Controlled Time Switch.In this switch the Buffer Memory and Control Memory are controlled write typei.e. the writing in it is controlled. The control function writes in the controlmemory at the location corresponding to the Incoming Time Slot Number, thelocation where it should be written in the Buffer Memory. Both these memoriesare sequential read type. Reading of control memory gives the address in theBuffer Memory for writing Incoming TS Byte. Thus reading of Buffer Memorysequentially the TS will be read from the location given by the Control Memory.Thus a one way Time switching has taken place. Similarly a both way switchingrequires two sets of such switches.

DUPLICATED SWITCHING: The switching is done in OCB-283 in two fully duplicated branchessimultaneously. For this purpose from each connection units the LR linksoriginate in two parallel branches towards two parallel sets of switching matricescalled SMX A and SMX B. The branches of such network are called A and Bbranches. Also the receive side LR links come from both the SMX’s A & B andare terminated on the respective connection units. The duplicated branches ofswitching have been designed to provide high reliability switching path for suchdiverse purposes as data switching, video conference, ISDN applications etc.With the duplicated paths of switching if there is error in one path the other pathwhich is good can be used continuous without interrupting the call in progress.

SAB FUNCTION: The connection units have their internal duplicated hardware whichis called Control Logic, which work in Pilot / Reserve arrangements. Also theyhave non duplicated hardware such as subscriber cards and PCM terminationcards. The duplicated LR’s originate from a function in connection units calledSAB-Selection And Amplification Of Branches. It’s role is to generate two sets ofLR’s in trans-direction with calculation of parity etc. In receive direction it getsdata from both the branches which it checks for parity and compares to detect anyerror in the two branches. In case of error the samples from only the good branchare taken after automatic testing of the quality of transmission of both thebranches by the common control and the faulty branch is withdrawn from theservice.The connection units lr links are formed into group of 8 LR’s at thefactory into cables with both ends terminated with plugs for the convenience ofinstallation. Such groups of LR’s are called GLR.

COMMON CHANNEL SIGNALLING NO.7: The latest signalling being implemented world wide is now the Common ChannelSignalling. This type of signalling is essential for the setting up of the ISDNnetwork.In this type of signalling the signalling information is sent from oneexchange to other exchange in the form of message coded in binary which isunderstandable by the intelligent devices available in both exchange. The CCITTorganization has recommended a standard protocol called CCITT signaling.The signalling message travels over a single Time Slot of the PCM connectingthe two exchange . This Time Slot is called Common Channel for signalling,hence the name Common Channel Signalling. The message over this commonchannel carry all relevant data for any other time slots circuits which carry voiceor subscriber data. The channels for subscribers are called Voice Channels.Signalling is often referred to as the Glue, which holds a network together. Itprovides the ability to transfer information between subscribers, within networksand between subscribers and networks. Without signalling, networks are inert. Byproviding effective signalling systems, a network is transformed into atremendously powerful medium through which subscribers can communicate witheach other using a range of telecommunications services.

What after M.E. in Digital Communication

Monday, September 24th, 2012

The scope of students who have finished their studies in Electronics and Communication is quite high as this is one of the most coveted branches of engineering. Students of Electronics and Communication can get work with fields like embedded systems, the telecom industry, and microprocessor manufacturers like Intel etc. Research labs for digital si

gnal processing also recruit students of Electronics and Communication.Besides this, it is also possible for them to get very challenging and much lucrative jobs with the IT sector. The DRDO, VSSC and BHEL are some organizations that take in students of Electronics and Communication for research and academic jobs when ever there are available vacancies.

Scope for Higher Studies after M.Tech in Electronics and Communication

Those who wish to pursue higher studies can go for Doctoral programs in any leading universities. To get admission into these programs, the students will need to appear for the GRE exam. As to appear for this exam, high marks will be needed by the aspirants.

Other Certification Courses after M.Tech in Electronics and Communication

From the many available options, students can also choose to go for certification programs. Not only will these programs supply students with more knowledge and experience, but also it will be of good help for them when they are in search for jobs. Some of the certification courses that students can join are:

  • Advanced Diploma in DSP System Design
  • Advanced Diploma in Embedded Systems Design
  • Advanced Diploma in Real Time Operating Systems
  • Advanced Diploma in VLSI Design
  • Advanced Diploma in Wireless Technology
  • Certificate in VLSI design engineering
  • Certification in Verilog and VHDL
  • Cisco Certified Network Associate Routing & Switching (CCNA) course
  • PG Diploma course in Industrial Automation System Design
  • Post Graduate Diploma in Wireless and Mobile Computing
  • Signaling & VoIP Protocol Implementation
  • Telecom Protocol Development

Career Opportunities after M.Tech in Electronics and Communication

Electronic engineers can gain entry into the various departments of the Indian government by appearing for some exams that are intended for them. Leading newspapers as well as web portals of the SSC and the UPSC will bring our announcements for the available posts and the details of the exams. The candidates can also join the defense services by writing the appropriate exams.   Those who pass the written part will be later required to attend an interview (physical and medical tests in addition to the interview in the case of defense services).

Some of the prospective employers of postgraduates of Electronics and Communications include:

  • Atomic Energy Commission
  • Central Electronics Limited
  • Defense services
  • Directorate General Posts and Telegraphs Departments
  • Hindustan Aeronautics Limited
  • Indian Railways
  • Ministry of Civil Aviation

Apart from the ones provided above, the career scope is quite broad for professionals in the field of Electronics and communication. Electronic Engineers can commence a business of their own by developing parts and other vital components for electronic goods. They can also start an assembly shop for repairing goods that become damaged. The best thing about doing a job like this is that they can make returns which may be much higher than that was invested originally. As to provide support as well as encouragement for people who start their own businesses, loan facilities are provided by banks as well as Small Scale Industries Development Corporations.

Nano Electronics

Wednesday, March 23rd, 2011

Nanoelectronics refer to the use of nanotechnology on electronic components, especially transistors. Although the term nanotechnology is generally defined as utilizing technology less than 100 nm in size, nanoelectronics often refer to transistor devices that are so small that inter-atomic interactions and quantum mechanical properties need to be studied extensively. As a result, present transistors do not fall under this category, even though these devices are manufactured with 45 nm, 32 nm or 22 nm technology.

Nanoelectronics are sometimes considered as disruptive technology because present candidates are significantly different from traditional transistors. Some of these candidates include: hybrid molecular/semiconductor electronics, one dimensional nanotubes/nanowires, or advanced molecular electronics.

Although nanoelectronic technology holds promise for the future, it is still under development and practical applications are unlikely to emerge in the near future.

Fundamental concepts

The volume of an object decreases as the third power of its linear dimensions, but the surface area only decreases as its second power. This somewhat subtle and unavoidable principle has huge ramifications. For example the power of a drill (or any other machine) is proportional to the volume, while the friction of the drill’s bearings and gears is proportional to their surface area. For a normal-sized drill, the power of the device is enough to handily overcome any friction. However, scaling its length down by a factor of 1000, for example, decreases its power by 10003 (a factor of a billion) while reducing the friction by only 10002 (a factor of “only” a million). Proportionally it has 1000 times less power per unit friction than the original drill. If the original friction-to-power ratio was, say, 1%, that implies the smaller drill will have 10 times as much friction as power. The drill is useless.

For this reason, while super-miniature electronic integrated circuits are fully functional, the same technology cannot be used to make working mechanical devices beyond the scales where frictional forces start to exceed the available power. So even though you may see microphotographs of delicately etched silicon gears, such devices are currently little more than curiosities with limited real world applications, for example, in moving mirrors and shutters. Surface tension increases in much the same way, thus magnifying the tendency for very small objects to stick together. This could possibly make any kind of “micro factory” impractical: even if robotic arms and hands could be scaled down, anything they pick up will tend to be impossible to put down. The above being said, molecular evolution has resulted in working cilia, flagella, muscle fibers and rotary motors in aqueous environments, all on the nanoscale. These machines exploit the increased frictional forces found at the micro or nanoscale. Unlike a paddle or a propeller which depends on normal frictional forces (the frictional forces perpendicular to the surface) to achieve propulsion, cilia develop motion from the exaggerated drag or laminar forces (frictional forces parallel to the surface) present at micro and nano dimensions. To build meaningful “machines” at the nanoscale, the relevant forces need to be considered. We are faced with the development and design of intrinsically pertinent machines rather than the simple reproductions of macroscopic ones.

All scaling issues therefore need to be assessed thoroughly when evaluating nanotechnology for practical applications.

Approaches to nanoelectronics


For example, single electron transistors, which involve transistor operation based on a single electron. Nanoelectromechanical systems also fall under this category. Nanofabrication can be used to construct ultradense parallel arrays of nanowires, as an alternative to synthesizing nanowires individually.

Nanomaterials electronics

Besides being small and allowing more transistors to be packed into a single chip, the uniform and symmetrical structure of nanotubes allows a higher electron mobility (faster electron movement in the material), a higher dielectric constant (faster frequency), and a symmetrical electron/hole characteristic.

Also, nanoparticles can be used as quantum dots.

Molecular electronics

Single molecule devices are another possibility. These schemes would make heavy use of molecular self-assembly, designing the device components to construct a larger structure or even a complete system on their own. This can be very useful for reconfigurable computing, and may even completely replace present FPGA technology.

Molecular electronics is a new technology which is still in its infancy, but also brings hope for truly atomic scale electronic systems in the future. One of the more promising applications of molecular electronics was proposed by the IBM researcher Ari Aviram and the theoretical chemist Mark Ratner in their 1974 and 1988 papers Molecules for Memory, Logic and Amplification, (see Unimolecular rectifier). This is one of many possible ways in which a molecular level diode / transistor might be synthesized by organic chemistry. A model system was proposed with a spiro carbon structure giving a molecular diode about half a nanometre across which could be connected by polythiophene molecular wires. Theoretical calculations showed the design to be sound in principle and there is still hope that such a system can be made to work.

Other approaches

Nanoionics studies the transport of ions rather than electrons in nanoscale systems.

Nanophotonics studies the behavior of light on the nanoscale, and has the goal of developing devices that take advantage of this behavior.

Nanoelectronic devices


Nanoradios have been developed structured around carbon nanotubes.


Nanoelectronics holds the promise of making computer processors more powerful than are possible with conventional semiconductor fabrication techniques. A number of approaches are currently being researched, including new forms of nanolithography, as well as the use of nanomaterials such as nanowires or small molecules in place of traditional CMOS components. Field effect transistors have been made using both semiconducting carbon nanotubes and with heterostructured semiconductor nanowires.

Energy production

Research is ongoing to use nanowires and other nanostructured materials with the hope to create cheaper and more efficient solar cells than are possible with conventional planar silicon solar cells. It is believed that the invention of more efficient solar energy would have a great effect on satisfying global energy needs.

There is also research into energy production for devices that would operate in vivo, called bio-nano generators. A bio-nano generator is a nanoscale electrochemical device, like a fuel cell or galvanic cell, but drawing power from blood glucose in a living body, much the same as how the body generates energy from food. To achieve the effect, an enzyme is used that is capable of stripping glucose of its electrons, freeing them for use in electrical devices. The average person’s body could, theoretically, generate 100 watts of electricity (about 2000 food calories per day) using a bio-nano generator. However, this estimate is only true if all food was converted to electricity, and the human body needs some energy consistently, so possible power generated is likely much lower. The electricity generated by such a device could power devices embedded in the body (such as pacemakers), or sugar-fed nanorobots. Much of the research done on bio-nano generators is still experimental, with Panasonic’s Nanotechnology Research Laboratory among those at the forefront.

Medical diagnostics

There is great interest in constructing nanoelectronic devices that could detect the concentrations of biomolecules in real time for use as medical diagnostics, thus falling into the category of nanomedicine. A parallel line of research seeks to create nanoelectronic devices which could interact with single cells for use in basic biological research. These devices are called nanosensors. Such miniaturization on nanoelectronics towards in vivo proteomic sensing should enable new approaches for health monitoring, surveillance, and defense technology.

NOTE: Reference Link

Integrated Circuit or Monolithic Integrated Circuit

Wednesday, March 23rd, 2011

An integrated circuit or monolithic integrated circuit (also referred to as IC, chip, and microchip) is an electronic circuit manufactured by diffusion of trace elements into the surface of a thin substrate of semiconductor material.

Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the world of electronics. Computers, cellular phones, and other digital appliances are now inextricable parts of the structure of modern societies, made possible by the low cost of production of integrated circuits.


Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using electronic components. The integrated circuit’s mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.

There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time. Furthermore, much less material is used to construct a packaged IC die than a discrete circuit. Performance is high since the components switch quickly and consume little power (compared to their discrete counterparts) because the components are small and positioned close together. As of 2006, chip areas range from a few square millimeters to around 350 mm2, with up to 1 million transistors per mm2.


Integrated circuit originally referred to a miniaturized electronic circuit consisting of semiconductor devices, as well as passive components bonded to a substrate or circuit board.This configuration is now commonly referred to as a hybrid integrated circuit. Integrated circuit has since come to refer to the single-piece circuit construction originally known as a monolithic integrated circuit.


Early developments of the integrated circuit go back to 1949, when the German engineer Werner Jacobi (Siemens AG) filed a patent for an integrated-circuit-like semiconductor amplifying device showing five transistors on a common substrate arranged in a 2-stage amplifier arrangement. Jacobi discloses small and cheap hearing aids as typical industrial applications of his patent. A commercial use of his patent has not been reported.

The idea of the integrated circuit was conceived by a radar scientist working for the Royal Radar Establishment of the British Ministry of Defence, Geoffrey W.A. Dummer (1909–2002), who published it at the Symposium on Progress in Quality Electronic Components in Washington, D.C. on May 7, 1952. He gave many symposia publicly to propagate his ideas. Dummer unsuccessfully attempted to build such a circuit in 1956.

A precursor idea to the IC was to create small ceramic squares (wafers), each one containing a single miniaturized component. Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which looked very promising in 1957, was proposed to the US Army by Jack Kilby, and led to the short-lived Micromodule Program (similar to 1951’s Project Tinkertoy). However, as the project was gaining momentum, Kilby came up with a new, revolutionary design: the IC.

Robert Noyce credited Kurt Lehovec of Sprague Electric for the principle of p-n junction isolation caused by the action of a biased p-n junction (the diode) as a key concept behind the IC.

Jack Kilby recorded his initial ideas concerning the integrated circuit in July 1958 and successfully demonstrated the first working integrated circuit on September 12, 1958. In his patent application of February 6, 1959, Kilby described his new device as “a body of semiconductor material … wherein all the components of the electronic circuit are completely integrated.” Kilby won the 2000 Nobel Prize in Physics for his part of the invention of the integrated circuit.

Robert Noyce also came up with his own idea of an integrated circuit half a year later than Kilby. Noyce’s chip solved many practical problems that Kilby’s had not. Noyce’s chip, made at Fairchild Semiconductor, was made of silicon, whereas Kilby’s chip was made of germanium.


In the early days of integrated circuits, only a few transistors could be placed on a chip, as the scale used was large because of the contemporary technology. As the degree of integration was small, the design was done easily. Later on, millions, and today billions, of transistors could be placed on one chip, and to make a good design became a task to be planned thoroughly. This gave rise to new design methods.


The first integrated circuits contained only a few transistors. Called “Small-Scale Integration” (SSI), digital circuits containing transistors numbering in the tens provided a few logic gates for example, while early linear ICs such as the Plessey SL201 or the Philips TAA320 had as few as two transistors. The term Large Scale Integration was first used by IBM scientist Rolf Landauer when describing the theoretical concept, from there came the terms for SSI, MSI, VLSI, and ULSI.

SSI circuits were crucial to early aerospace projects, and vice-versa. Both the Minuteman missile and Apollo program needed lightweight digital computers for their inertial guidance systems; the Apollo guidance computer led and motivated the integrated-circuit technology,while the Minuteman missile forced it into mass-production. The Minuteman missile program and various other Navy programs accounted for the total $4 million integrated circuit market in 1962, and by 1968, U.S. Government space and defense spending still accounted for 37% of the $312 million total production. The demand by the U.S. Government supported the nascent integrated circuit market until costs fell enough to allow firms to penetrate the industrial and eventually the consumer markets. The average price per integrated circuit dropped from $50.00 in 1962 to $2.33 in 1968. Integrated Circuits began to appear in consumer products by the turn of the decade, a typical application being FM inter-carrier sound processing in television receivers.

The next step in the development of integrated circuits, taken in the late 1960s, introduced devices which contained hundreds of transistors on each chip, called “Medium-Scale Integration” (MSI).

They were attractive economically because while they cost little more to produce than SSI devices, they allowed more complex systems to be produced using smaller circuit boards, less assembly work (because of fewer separate components), and a number of other advantages.

Further development, driven by the same economic factors, led to “Large-Scale Integration” (LSI) in the mid 1970s, with tens of thousands of transistors per chip.

Integrated circuits such as 1K-bit RAMs, calculator chips, and the first microprocessors, that began to be manufactured in moderate quantities in the early 1970s, had under 4000 transistors. True LSI circuits, approaching 10000 transistors, began to be produced around 1974, for computer main memories and second-generation microprocessors.


The final step in the development process, starting in the 1980s and continuing through the present, was “very large-scale integration” (VLSI). The development started with hundreds of thousands of transistors in the early 1980s, and continues beyond several billion transistors as of 2009.

Multiple developments were required to achieve this increased density. Manufacturers moved to smaller rules and cleaner fabs, so that they could make chips with more transistors and maintain adequate yield. The path of process improvements was summarized by the International Technology Roadmap for Semiconductors (ITRS). Design tools improved enough to make it practical to finish these designs in a reasonable time. The more energy efficient CMOS replaced NMOS and PMOS, avoiding a prohibitive increase in power consumption. Better texts such as the landmark textbook by Mead and Conway helped schools educate more designers, among other factors.

In 1986 the first one megabit RAM chips were introduced, which contained more than one million transistors. Microprocessor chips passed the million transistor mark in 1989 and the billion transistor mark in 2005. The trend continues largely unabated, with chips introduced in 2007 containing tens of billions of memory transistors.


To reflect further growth of the complexity, the term ULSI that stands for “ultra-large-scale integration” was proposed for chips of complexity of more than 1 million transistors.

Wafer-scale integration (WSI) is a system of building very-large integrated circuits that uses an entire silicon wafer to produce a single “super-chip”. Through a combination of large size and reduced packaging, WSI could lead to dramatically reduced costs for some systems, notably massively parallel supercomputers. The name is taken from the term Very-Large-Scale Integration, the current state of the art when WSI was being developed.

A system-on-a-chip (SoC or SOC) is an integrated circuit in which all the components needed for a computer or other system are included on a single chip. The design of such a device can be complex and costly, and building disparate components on a single piece of silicon may compromise the efficiency of some elements. However, these drawbacks are offset by lower manufacturing and assembly costs and by a greatly reduced power budget: because signals among the components are kept on-die, much less power is required (see Packaging).

A three-dimensional integrated circuit (3D-IC) has two or more layers of active electronic components that are integrated both vertically and horizontally into a single circuit. Communication between layers uses on-die signaling, so power consumption is much lower than in equivalent separate circuits. Judicious use of short vertical wires can substantially reduce overall wire length for faster operation.

Advances in integrated circuits

The die from an Intel 8742, an 8-bit microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip.

Among the most advanced integrated circuits are the microprocessors or “cores“, which control everything from computers and cellular phones to digital microwave ovens. Digital memory chips and ASICs are examples of other families of integrated circuits that are important to the modern information society. While the cost of designing and developing a complex integrated circuit is quite high, when spread across typically millions of production units the individual IC cost is minimized. The performance of ICs is high because the small size allows short traces which in turn allows low power logic (such as CMOS) to be used at fast switching speeds.

ICs have consistently migrated to smaller feature sizes over the years, allowing more circuitry to be packed on each chip. This increased capacity per unit area can be used to decrease cost and/or increase functionality—see Moore’s law which, in its modern interpretation, states that the number of transistors in an integrated circuit doubles every two years. In general, as the feature size shrinks, almost everything improves—the cost per unit and the switching power consumption go down, and the speed goes up. However, ICs with nanometer-scale devices are not without their problems, principal among which is leakage current (see subthreshold leakage for a discussion of this), although these problems are not insurmountable and will likely be solved or at least ameliorated by the introduction of high-k dielectrics. Since these speed and power consumption gains are apparent to the end user, there is fierce competition among the manufacturers to use finer geometries. This process, and the expected progress over the next few years, is well described by the International Technology Roadmap for Semiconductors (ITRS).

In current research projects, integrated circuits are also developed for sensoric applications in medical implants or other bioelectronic devices. Particular sealing strategies have to be taken in such biogenic environments to avoid corrosion or biodegradation of the exposed semiconductor materials. As one of the few materials well established in CMOS technology, titanium nitride TiN turned out as exceptionally stable and well suited for electrode applications in medical implants.


Integrated circuits can be classified into analog, digital and mixed signal (both analog and digital on the same chip).

Digital integrated circuits can contain anything from one to millions of logic gates, flip-flops, multiplexers, and other circuits in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. These digital ICs, typically microprocessors, DSPs, and micro controllers work using binary mathematics to process “one” and “zero” signals.

Analog ICs, such as sensors, power management circuits, and operational amplifiers, work by processing continuous signals. They perform functions like amplification, active filtering, demodulation, mixing, etc. Analog ICs ease the burden on circuit designers by having expertly designed analog circuits available instead of designing a difficult analog circuit from scratch.

ICs can also combine analog and digital circuits on a single chip to create functions such as A/D converters and D/A converters. Such circuits offer smaller size and lower cost, but must carefully account for signal interference.



The semiconductors of the periodic table of the chemical elements were identified as the most likely materials for a solid state vacuum tube. Starting with copper oxide, proceeding to germanium, then silicon, the materials were systematically studied in the 1940s and 1950s. Today, silicon monocrystals are the main substrate used for integrated circuits (ICs) although some III-V compounds of the periodic table such as gallium arsenide are used for specialized applications like LEDs, lasers, solar cells and the highest-speed integrated circuits. It took decades to perfect methods of creating crystals without defects in the crystalline structure of the semiconducting material.

Semiconductor ICs are fabricated in a layer process which includes these key process steps:

  • Imaging
  • Deposition
  • Etching

The main process steps are supplemented by doping and cleaning.

Mono-crystal silicon wafers (or for special applications, silicon on sapphire or gallium arsenide wafers) are used as the substrate. Photolithography is used to mark different areas of the substrate to be doped or to have polysilicon, insulators or metal (typically aluminium) tracks deposited on them.

  • Integrated circuits are composed of many overlapping layers, each defined by photolithography, and normally shown in different colors. Some layers mark where various dopants are diffused into the substrate (called diffusion layers), some define where additional ions are implanted (implant layers), some define the conductors (polysilicon or metal layers), and some define the connections between the conducting layers (via or contact layers). All components are constructed from a specific combination of these layers.
  • In a self-aligned CMOS process, a transistor is formed wherever the gate layer (polysilicon or metal) crosses a diffusion layer.
  • Capacitive structures, in form very much like the parallel conducting plates of a traditional electrical capacitor, are formed according to the area of the “plates”, with insulating material between the plates. Capacitors of a wide range of sizes are common on ICs.
  • Meandering stripes of varying lengths are sometimes used to form on-chip resistors, though most logic circuits do not need any resistors. The ratio of the length of the resistive structure to its width, combined with its sheet resistivity, determines the resistance.
  • More rarely, inductive structures can be built as tiny on-chip coils, or simulated by gyrators.

Since a CMOS device only draws current on the transition between logic states, CMOS devices consume much less current than bipolar devices.

A random access memory is the most regular type of integrated circuit; the highest density devices are thus memories; but even a microprocessor will have memory on the chip. Although the structures are intricate – with widths which have been shrinking for decades – the layers remain much thinner than the device widths. The layers of material are fabricated much like a photographic process, although light waves in the visible spectrum cannot be used to “expose” a layer of material, as they would be too large for the features. Thus photons of higher frequencies (typically ultraviolet) are used to create the patterns for each layer. Because each feature is so small, electron microscopes are essential tools for a process engineer who might be debugging a fabrication process.

Each device is tested before packaging using automated test equipment (ATE), in a process known as wafer testing, or wafer probing. The wafer is then cut into rectangular blocks, each of which is called a die. Each good die (plural dice, dies, or die) is then connected into a package using aluminium (or gold) bond wires which are welded and/or Thermosonic Bonded to pads, usually found around the edge of the die. After packaging, the devices go through final testing on the same or similar ATE used during wafer probing. Test cost can account for over 25% of the cost of fabrication on lower cost products, but can be negligible on low yielding, larger, and/or higher cost devices.

As of 2005, a fabrication facility (commonly known as a semiconductor fab) costs over $1 billion to construct, because much of the operation is automated. The most advanced processes employ the following techniques:


The earliest integrated circuits were packaged in ceramic flat packs, which continued to be used by the military for their reliability and small size for many years. Commercial circuit packaging quickly moved to the dual in-line package (DIP), first in ceramic and later in plastic. In the 1980s pin counts of VLSI circuits exceeded the practical limit for DIP packaging, leading to pin grid array (PGA) and leadless chip carrier (LCC) packages. Surface mount packaging appeared in the early 1980s and became popular in the late 1980s, using finer lead pitch with leads formed as either gull-wing or J-lead, as exemplified by small-outline integrated circuit — a carrier which occupies an area about 30 – 50% less than an equivalent DIP, with a typical thickness that is 70% less. This package has “gull wing” leads protruding from the two long sides and a lead spacing of 0.050 inches.

In the late 1990s, plastic quad flat pack (PQFP) and thin small-outline package (TSOP) packages became the most common for high pin count devices, though PGA packages are still often used for high-end microprocessors. Intel and AMD are currently transitioning from PGA packages on high-end microprocessors to land grid array (LGA) packages.

Ball grid array (BGA) packages have existed since the 1970s. Flip-chip Ball Grid Array packages, which allow for much higher pin count than other package types, were developed in the 1990s. In an FCBGA package the die is mounted upside-down (flipped) and connects to the package balls via a package substrate that is similar to a printed-circuit board rather than by wires. FCBGA packages allow an array of input-output signals (called Area-I/O) to be distributed over the entire die rather than being confined to the die periphery.

Traces out of the die, through the package, and into the printed circuit board have very different electrical properties, compared to on-chip signals. They require special design techniques and need much more electric power than signals confined to the chip itself.

When multiple dies are put in one package, it is called SiP, for System In Package. When multiple dies are combined on a small substrate, often ceramic, it’s called an MCM, or Multi-Chip Module. The boundary between a big MCM and a small printed circuit board is sometimes fuzzy.

Chip labeling and manufacture date

Most integrated circuits large enough to include identifying information include four common sections: the manufacturer’s name or logo, the part number, a part production batch number and/or serial number, and a four-digit code that identifies when the chip was manufactured. Extremely small surface mount technology parts often bear only a number used in a manufacturer’s lookup table to find the chip characteristics.

The manufacturing date is commonly represented as a two-digit year followed by a two-digit week code, such that a part bearing the code 8341 was manufactured in week 41 of 1983, or approximately in October 1983.

Legal protection of semiconductor chip layouts

Like most of the other forms of intellectual property, IC layout designs are creations of the human mind. They are usually the result of an enormous investment, both in terms of the time of highly qualified experts, and financially. There is a continuing need for the creation of new layout-designs which reduce the dimensions of existing integrated circuits and simultaneously increase their functions. The smaller an integrated circuit, the less the material needed for its manufacture, and the smaller the space needed to accommodate it. Integrated circuits are utilized in a large range of products, including articles of everyday use, such as watches, television sets, washing machines, automobiles, etc., as well as sophisticated data processing equipment.

The possibility of copying by photographing each layer of an integrated circuit and preparing photomasks for its production on the basis of the photographs obtained is the main reason for the introduction of legislation for the protection of layout-designs.

A diplomatic conference was held at Washington, D.C., in 1989, which adopted a Treaty on Intellectual Property in Respect of Integrated Circuits (IPIC Treaty). The Treaty on Intellectual Property in respect of Integrated Circuits, also called Washington Treaty or IPIC Treaty (signed at Washington on May 26, 1989) is currently not in force, but was partially integrated into the TRIPs agreement.

National laws protecting IC layout designs have been adopted in a number of countries.

Other developments

In the 1980s, programmable integrated circuits were developed. These devices contain circuits whose logical function and connectivity can be programmed by the user, rather than being fixed by the integrated circuit manufacturer. This allows a single chip to be programmed to implement different LSI-type functions such as logic gates, adders and registers. Current devices named FPGAs (Field Programmable Gate Arrays) can now implement tens of thousands of LSI circuits in parallel and operate up to 1.5 GHz (Achronix holding the speed record).

The techniques perfected by the integrated circuits industry over the last three decades have been used to create microscopic machines, known as MEMS. These devices are used in a variety of commercial and military applications. Example commercial applications include DLP projectors, inkjet printers, and accelerometers used to deploy automobile airbags.

In the past, radios could not be fabricated in the same low-cost processes as microprocessors. But since 1998, a large number of radio chips have been developed using CMOS processes. Examples include Intel’s DECT cordless phone, or Atheros’s 802.11 card.

Future developments seem to follow the multi-core multi-microprocessor paradigm, already used by the Intel and AMD dual-core processors. Intel recently unveiled a prototype, “not for commercial sale” chip that bears 80 microprocessors. Each core is capable of handling its own task independently of the others. This is in response to the heat-versus-speed limit that is about to be reached using existing transistor technology. This design provides a new challenge to chip programming. Parallel programming languages such as the open-source X10 programming language are designed to assist with this task.

Silicon labelling and graffiti

To allow identification during production most silicon chips will have a serial number in one corner. It is also common to add the manufacturer’s logo. Ever since ICs were created, some chip designers have used the silicon surface area for surreptitious, non-functional images or words. These are sometimes referred to as Chip Art, Silicon Art, Silicon Graffiti or Silicon Doodling.

Notable ICs


NOTE: Reference link  .

Printed Circuit Board

Wednesday, March 23rd, 2011

Sometimes abbreviated PCB, a thin plate on which chips and other electronic components are placed. Computers consist of one or more boards, often called cards or adapters. Circuit boards fall into the following categories:

  • motherboard : The principal board that has connectors for attaching devices to the bus. Typically, the mother board contains the CPU, memory, and basic controllers for the system. On PCs, the motherboard is often called the system board or mainboard.
  • expansion board : Any board that plugs into one of the computer’s expansion slots. Expansion boards include controller boards, LAN cards, and video adapters.
  • Daughtercard : Any board that attaches directly to another board.
  • controller board: A special type of expansion board that contains a controller for a peripheral device. When you attach new devices, such as a disk drive or graphics monitor, to a computer, you often need to add a controller board.
  • Network Interface Card (NIC) : An expansion board that enables a PC to be connected to a local-area network (LAN).
  • video adapter: An expansion board that contains a controller for a graphics monitor.
  • Printed circuit boards are also called cards.