What are different categories of antenna and give an example of each?

Different categories of antenna are as follows :

1. Wire Antennas - Short Dipole Antenna2. Microstrip Antennas - Rectangular Microstrip (Patch) Antennas3. Reflector Antennas - Corner Reflector4. Travelling Wave Antennas - Helical Antennas5. Aperture Antennas - Slot Antenna6. Other Antennas - NFC Antennas

What is handover and what are its types?

Handover in mobile communication refers to the process of transferring a call from one network cell to another without breaking the call.There are two types of handover which are as follows :

Hard Handoff : hard handoff is the process in which the cell connection is disconnected from the previous cell before it is made with the new one.

Soft Handoff : It is the process in which a new connection is established first before disconnecting the old one. It is thus more efficient and smart.

What is ionospheric bending?

When a radio wave travels into the ionospheric layer it experiences refraction due to difference in density. The density of ionospheric layer is rarer than the layer below which causes the radio wave to be bent away from the normal. Also the radio wave experiences a force from the ions in the ionospheric layer. If incident at the correct angle the radio wave is completely reflected back to the inner atmosphere due to total internal reflection. This phenomenon is called ionospheric reflection and is used in mobile communication for radio wave propagation also known as ionospheric bending of radio waves.

What is CDMA?

CDMA stands for Code Division Multiple Access which uses digital format. In CDMA systems several transmissions via the radio interface take place simultaneously on the same frequency bandwidth. User data is combined at the transmitter’s side with a code, then transmitted. On air, all transmission get mixed. At the receiver's side the same code is used as in the transmitter’s side. The code helps the receiver to filter the user information of the transmitter from incoming mixture of all transmissions on the same frequency band and same time.

Explain the concept of frequency re-use.

The whole of the geographical area is divided into hexagonal shape geometrical area called cell and each cell having its own transceiver. Each BTS (cell site) allocated different band of frequency or different channel. Each BTS antenna is designed in such a way that i cover cell area in which it is placed with frequency allotted without interfering other cell signals. The design process of selecting and allocating channel groups for all of the cellular base station within system is called frequency reuse.

Explain Bluetooth.

Bluetooth is designed to be a personal area network, where participating entities are mobile and require sporadic communication with others. It is omni directional i.e. it does not have line of sight limitation like infra red does. Ericsson started the work on Bluetooth and named it after the Danish king Harold Biuetooth. Bluetooth operates in the 2.4 GHz area of spectrum and provides a range of 10 metres. It offers transfer speeds of around 720 Kbps.

7. What are GPRS services?

GPRS services are defined to fall in one of the two categories :

- PTP ( Point to point)- PTM ( Point to Multipoint)Some of the GPRS services are not likely to be provided by network operators during early deployment of GPRS due in part to the phased development of standard. Market demand is another factor affecting the decision of operators regarding which services to offer first.

8. What are the advantages of CDMA?

Advantages of CDMa are as follows :

1. Frequency diversity : Transmission is spread out over a large bandwidth due to that less affected by noise. If bandwidth is increased S/N ratio increases, which means noise will be reduced.2. Multiplication Resistance : Chipping codes used for CDMA not only exhibit low correlation but also low autocorrelation. Hence a version of the signal that is delayed by more than one chip interval does not interfere with dominant signal as in other multipath environments.3. Privacy : Due to spread spectrum is obtained by the use of noise like signals, where each user has a unique code, so privacy is inherent.4. Graceful Degradation. In CDMA, more users access the system simultaneously as compared to FDMa, TDMA.

9. What are the advantages of spread spectrum?

SPread spectrum has the following advantages :

1. No crosstalk interference.2. Better voice quality/data integrity and less static noise.3. Lowered susceptibility to multipath fading.4. Inherent security.5. Co-existence.6. Longer operating distances.7. Hard to detect.8. Hard to intercept or demodulate.9. Harder to jam than narrow bands.10. Use of ranging and radar.

10. Explain the steps involved in demodulating a signal.

Once the signal is coded, modulated and then sent, the receiver must demodulate the signal. This is usually done in two steps :1. Spectrum spreading (e.g., direct sequence or frequency hopping) modulation is removed.2. The remaining information bearing signal is demodulated by multiplying with a local reference identical in structure and synchronised with received signal.

11. How can a Pseudo Random Noise COde be usable?

To be usable for direct sequence spreading, a PN code must meet the following conditions :

1. Sequence must be built from 2 levelled numbers.2. The codes must have sharp autocorrelation peak to enable code synchronization.3. Codes must have a low cross-correlation value, the lower it is, more are the number of users which can be allowed in the system.4. The codes should be “balanced” i.e. the difference between ones and zeros in code may only be 1.

12. What are the drawbacks of walsh codes?

Walsh codes have the following drawbacks :

1. The codes do not have a single, narrow autocorrelation peak.2. The spreading is not over the whole bandwidth; instead the energy is spread over a number of discrete frequency components.3. Although the full sequence cross correlation is identically zero, this does not hold for a partial sequence cross correlation function. Thus advantage of using orthogonal codes is lost.4. Orthogonality is also affected by channel properties like multi path.

13. Explain radio environment in building.

Building penetration : Building penetration depends on the material used for construction and architecture used. This varies building to building and is based on building construction.Building Height Effect : The signal strength is always higher at top floor and generally floor gain height is about 2.7dB/floor which is not dependent on building construction.Building Floor Reception : The signal isolation between floors in a multi floor building is on the average about 20dB. Within a floor of 150 * 150 feet, the propagation loss due to interior walls, depending on the wall materials is about 20 dB between the strong and the weak areas.

14. List some advantages of GSM.

Here are some advantages of GSM :1. GSM is mature, this maturity means a more stable network with robust features.2. Less signal deterioration inside buildings.3. Ability to use repeaters.4. Talk time is generally higher in GSM phones due to pulse nature of transmission.5. The availability of Subscriber Identity Modules allows users to switch networks and handset at will.6. GSM covers virtually all parts of world so international roaming is not a problem.

15. What are the various types of numbers for network identity?

Various types of number for network identity are as follows :1. MSISDN ( Mobile station ISDN) Number : It is international mobile subscriber number which is normally called mobile number. It is unique worldwide.2. MSRN ( Mobile Subscriber Routing Number) : MSRN is used during mobile terminate trunk call to provide location of mobile subscriber.3. HON ( Hand Over Number ) : HON is used for providing information required to transfer call from one B?SC to another BSC or to another MSC.4. ISMI ( International Mobile Subscriber Identity Number) : Purpose of ISMI is for location update and authentication.5. TMSI ( Temporary Mobile Subscriber Identity ) : TMSI is used instead of IMSI to improve security efficiency of network.6. IMEI : International Mobile Equipment Identity.

16. What are the functions of Base Station System ( BSS)?

Functions of BSS are as follows :1. Radio path control.2. BTS and TC control.3. Connection establishment with MS-NSS.4. Mobility management, speech transcoding.5. Connection of statistical data.

17. What are the parts of Network Management System ( NMS )?

Following are the parts of network management system :1. OMC : Operation and maintenance center - Computerized monitoring center.2. NMC : Network Management Center - Centralized control of a network is done here.3. OSS : Operation and support system - Used for supporting activities performed in an OMC and/or NMC.

18. What are applications of DSP?

Some selected applications or digital signal processing that are often encountered in daily life are listed as follows:1. Telecommunication: Echo cancellation in telephone networks.2. Military Radar signal processing3. Consumer electronics Digital Audio/TV4. Instrumentation and control5. Image processing image representation, image compression6. Speech processing speech analysis methods are used in automatic speech recognition7. Medicine Medical diagnostic instrumentation such as computerised tomography (CT)8. Seismology DSP techniques are employed in geophysical exploration for oil and gas.9. Signal Filtering Removal of unwanted background noise.

19. What is analog-to-digital conversion of signals?

A discrete-time signal is defined by specifying its value only at discrete times, called sampling instants. When the sampled values are quantised and encoded, a digital signal is obtained. A digital signal is obtained from the analog signal by using an analog-to-digital converter. This entire process is referred to as the conversion of signals from analog to digital form.

20. What are the properties of ROC for z-Transform?

Properties of the ROC for the z-Transform :1. X(z) converges uniformly if and only if the ROC of the z-transform X(z) of the sequence includes the unit circle. The ROC of X(z) consists of a ring in the z-plane centered about the origin. That is, the ROC of the z-transform of x(n) has values of z for which x(n) r-n is absolutely summable.2. The ROC does not contain any poles.3. When x(n) is of finite duration then the ROC is the entire z-plane, except possibly z=0 and/or z=infinity.4. If x(n) is a right sided sequence, the ROC will not include infinity.5. If x(n) is a left sided sequence, the ROC will not include z=0. However if x(n)=0 for all n>0, the ROC will include z=0.6. If x(n) is two sided and if the circle |z| = r0 is in the ROC, then the ROC will consist of a ring in the z-plane that includes the circle |z|=r0.7. If X(z) is rational, then the ROC extends to infinity, i.e. the ROC is bounded by poles.8. If x(n) is causal, then the ROC includes z=infinity.9. If x(n) is anti- causal, trhen the ROC includes z=0.

1. What is DMA controller?2. What is DMA channels?3. What happens during DMA transfer? 4. What is half duplex transmission?5. What is the difference between the bandwidth of half duplex and simplex transmission?6. What are the processes required to perform interfacing successfully?7. What is single input output interface? How it is different from single ended interface?8. How does data transfer takes place between memory and input output ports?9. What is parallel data transfer process?10. Differentiate between PPI and input output devices.11. What is parallel to serial conversion?12. Explain the working of stepping motors.13. What are the data pins of microprocessors? What is their use?14. What is working principle of Profibus and how it transfer data?15. Explain zener breakdown and avalanche breakdown?16. What is the need of filtering ideal response of filters and actual response of filters? What is sampling theorem? What is impulse response?17. What are advantages of dc supply over ac supply?18. What is the voltage level of noise signal?19. What happens when a magnetic material is heated strongly?20. What is the effect of polarization of dielectric under heat?21. Which number system is used in analysing and programming of microprocessors?22. What happens when an inverter is placed between both inputs of S-K flip flop?23. What is the chief characterstic of master-slave flip flop?24. What logic function is obtained by adding an inverter to the output of an AND gate?25. Which register which contains the instruction that is to be executed?26. Which is used as storage location in the ALU and the control section of a computer?27. What is simulator programme?28. In C programming language, how many parameters can be passed to a function ?29. Which filter has the highest Q factor?30. What is multiplexing? Explain its primary advantage.31. What is SSB modulation?32. How can we remove unwanted sideband from SSB modulation?33. How many channels are there in 2MB pulse code modulation?34. What is cut off frequency?35. Differentiate between pass band and stop band.36. Explain Shanon-hartley law.37. Why interlacing is used in television?38. Which type of modulation is used in TV transmission?39. What is attenuation?40. Differentiate between transducer and transponder.41. What is op-amp?42. Differentiate between conductor and inductor.43. What is meant by pre-emphasis and de-emphasis?44. Which semiconductor device is used as a voltage regulator and why?45. What are monitoring methods for Electronics activities?46. What is an interrupt?

Electronics and communication engineering core interview questions1: What is difference between Microprocessor and Microcontroller ?

2: Why is Zener Diode always used in Reverse Bias condition ? 

3: Difference between FM and AM, which is preferred & its advantages. 

4: Questions on different coding techniques ?

5: Questions on signal processing techniques ?

6: What is RS in RS-232 ?

7: What is Lenz law ?

8: What is Transmission Frequency of Bluetooth, Wi-Fi and Wi-MAX ?

9: What is difference between Piconet and Scatternet ?

10: What is Moore's Law ?

11: How many satellites comprise the GPS and expand it ? 

12: What is ZigBee and its specifications ?

13: What is FPGA ?

14: What is MIMO ?

15: What is VOIP ?

16: On what principle do Transformers work ?

17: What is EDFA ?

18: What are different types of antennas ?

19: What is Yagi-Uda antenna ?

20: What is latest satellite from ISOR ?

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why the input resistance of an op-amp is high whereas it's output resistance is low?A.Loading at the input point and to pass the maximum output to the load is the requirement of Op-Amp which is a current exchange device from input side to output side.

Q.what do you understand by microwaves? why these are called microA.micro waves are those waves whose wavelength is less than a foot(30 cms) or freq ranging from 1 GHz to 1000 GHz.Because of there tinyness these are called micro.

Q. how do microwave oven works??A. Heart of microwave oven is magnatron which generates frequency of appox. 2.4 GHz.explain working of magnatron.

Q.What is CMRR? Explain briefly.A. CMRR stands for common mode rejection ratio. It is a measure of the ability of a test instrument to reject interference that is common to both of its measurement input terminals. It is expressed in decibels and it is the ratio of the actual or common signal level appearing on the two input terminals together to the measured level.

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1. What is meant by D-FF? D Flip Flop (or did you mean to ask its working?)

2. What is the basic difference between Latches and Flip flops? (Latches do not store information, here, a bit)

3. What is a multiplexer?

4. How can you convert an SR Flip-flop to a JK Flip-flop?

5. How can you convert an JK Flip-flop to a D Flip-flop?

6. What is Race-around problem? How can you rectify it?

7. Which semiconductor device is used as a voltage regulator and why? (zener diode in reverse bias, why because it allows for a large variation in current for a negligible variation in voltage)

8. What do you mean by an ideal voltage source? (Sources infinite current to any load without any change in o/p voltage)

9. What do you mean by zener breakdown and avalanche breakdown?

10. What are the different types of filters? (low pass, high pass, band pass, band stop, resonant)

11. What is the need of filtering ideal response of filters and actual response of filters?

12. What is sampling theorem? (minium 2 samples per time period? not too sure of this)

13. What is impulse response?

14. Explain the advantages and disadvantages of FIR filters compared to IIR counterparts.

15. What is CMRR? Explain briefly.  (explained by someone a few posts above)

16. What do you mean by half-duplex and full-duplex communication? Explain briefly.  (half duplex - both sender & receiver can communicate with each other, but not simultaneously...full duplex - same but simultaneous communication possible)

17. Which range of signals are used for terrestrial transmission?

18. What is the need for modulation? (transmitting over a distance, encryption?)

19. Which type of modulation is used in TV transmission?

20. Why we use vestigial side band (VSB-C3F) transmission for picture?

21. When transmitting digital signals is it necessary to transmit some harmonics in addition to fundamental frequency?

22. For asynchronous transmission, is it necessary to supply some synchronizing pulses additionally or to supply or to supply start and stop bit?

23. BPFSK is more efficient than BFSK in presence of noise. Why?

24. What is meant by pre-emphasis and de-emphasis?

25. What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB? (3dB is the half power value)

26. What do you mean by ASCII, EBCDIC?

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1. What is meant by D-FF?(D-flip flop stands for Delay flip-flop, it delays input by one clock pulse)

2. What is the basic difference between Latches and Flip flops?(Latches are monostable and flip-flops are bistable)

3. What is a multiplexer?(It is used to multiplex data from different sources normally used in TDM)

4. How can you convert an SR Flip-flop to a JK Flip-flop?

5. How can you convert an JK Flip-flop to a D Flip-flop?( Connect J to D and K to not(D))

6. What is Race-around problem? How can you rectify it?( Race around condition occurs in a JK flip-flop when both the inputs are set to '1', it can be rectified using edge-triggered flip-flop or using master-slave flip-flops)

7. Which semiconductor device is used as a voltage regulator and why?

8. What do you mean by an ideal voltage source?

9. What do you mean by zener breakdown and avalanche breakdown?( zener breakdown takes place when very high voltage is applied to the diode this results in very high reverse current, as voltage is further increased minority carriers gain further momentum and strike atoms releases more carriers, which results in further increase in temp. It becomes vicious cycle and leads to avalanche breakdown or on other words "thermal runaway".

10. What are the different types of filters?( analog filters n digital filters not sure wht u meant)

11. What is the need of filtering ideal response of filters and actual response of filters?

12. What is sampling theorem?( sampling frequency should be atleast twice the maximum freq present in the signal)

13. What is impulse response?( response given by a digital system when impulse signal is applied to it. Used to find out stability of system) 

14. Explain the advantages and disadvantages of FIR filters compared to IIR counterparts.

15. What is CMRR? Explain briefly.( Common mode rejection ratio)

16. What do you mean by half-duplex and full-duplex communication? Explain briefly.( half-duplex: either sender or receiver can use the channel at one time eg walky-talky and full-duplex: sender or receiver or both can use the channel at one time eg telephone)

17. Which range of signals are used for terrestrial transmission?

18. What is the need for modulation?

19. Which type of modulation is used in TV transmission?( video signal: vestigial side band modulation and audio signal: FM)

20. Why we use vestigial side band (VSB-C3F) transmission for picture?( why not DSBSC: large bandwidth req.why not SSBSC: To over come distortion by filters used at receivers thus demodulation becomes complex hence costly)

21. When transmitting digital signals is it necessary to transmit some harmonics in addition to fundamental frequency?( yup but not sure why)

22. For asynchronous transmission, is it necessary to supply some synchronizing pulses additionally or to supply or to supply start and stop bit?( for asyn tx it is necessary to use start and stop bits as no common clock is there)

23. BPFSK is more efficient than BFSK in presence of noise. Why?

24. What is meant by pre-emphasis and de-emphasis?( used in TV Tx for voice signal not sure why)

25. What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?

26. What do you mean by ASCII, EBCDIC?

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Hello puys,

I am posting some of the imp questions subject wise:

Following r some imp topics:Semiconductor devices and circuits:

Resistance, inductance(dc short, ac open), capacitance (ac short , dc open)

Diodes:types& definitions: p-n, zener(zener breakdown, voltage regulator),tunnel (tunneling effect),varactor,Impatt,Trapatt, gunn, pin;

Transistors:two types 1. Based on minority carrier(BJT:npn,pnp) 2. based on FET principle(IGFET,JFET,MOSFET,MESFET);

Amplifiers:types:LNA,Power amp,feedback,balanced,distributed amp

Active state (for CE conf):Base if FB and collector is RB:Saturation:Both bas and collector are FBCut-off:Both bas and collector are RB

Untuned Amp:Class A,B,AB,C

Oscillator:total phase shift at input is 0 or multiples of 2pi.

MPMC:

MP are memoryless.General purpose processorsMC have inbuilt memory and IO portsto interface MP with ports 825 is used

MP types: 8085 (8-data, 16 address);8086(16data,16 address); 80186(16 data, 20 adddress); 80286(16 data, 24 address);80386(16 data, 32 address);80486 (32 data, 32 address); pentium (64 data, 32 address,Pipelining,More segmentations&memory banks);Pentium Pro(64 data,36 address)

MC: 4K rom, 128 bytes ram,2 timers,4 io ports,1 serial port, 8 bit cpu, 16 address lines, 40 pins

Control systems:

Definitions:System:A no of elements are connected in a sequence to perform a specific function is called a system.

Control system: system in which o/p is controlled by i/p.Open loop system(o/p does not change automatically)& closed loop system (output changes automatically)

Stability:BIBO condition :i/p=0 then o/p tends to 0.

Limtedly stable,absolutely stable and conditionally stable:

Three ways to check stability: Routh-herwitz criteria, nyquist criteria, root locus method

PS: Will be posting topics of other subjects soon.

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1.What are the flags in 8086?

Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.

2.What are the various interrupts in 8086??

Maskable interrupts, Non-Maskable interrupts

3.What is meant by Maskable interrupts? 

An interrupt that can be turned off by the programmer is known as Maskable interrupt.

4.Which interrupts are generally used for critical events??

Non-Maskable interrupts are used in critical events Such as Power failure, Emergency, Shut off etc.

5.What is the Maximum clock frequency in 8086?

5 Mhz is the Maximum clock frequency in 8086.

6.What are the various segment registers in 8086?

Code, Data, Stack, Extra 

7.Which Stack is used in 8086?

FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first. 

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1.What are the various registers in 8085? 

Accumulator register, Temporary register, Instruction register, Stack Pointer, Program Counter are the various registers in 8085 .

2.What is Stack Pointer

Stack pointer is a special purpose 16-bit register in the Microprocessor, which holds the address of the top of the stack

3.What is Program counter? 

Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.

4.Which Stack is used in 8085? 

LIFO (Last In First Out) stack is used in 8085.In this type of Stack the last stored information can be retrieved first.

5.What is meant by a bus? 

A bus is a group of conducting lines that carriers data, address, & control signals.

6.What is Tri-state logic? 

Three Logic Levels are used and they are High, Low, High impedance state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions. Tri-state logic has a third line called enable line.

7.Give an example of one address microprocessor?

8085 is a one address microprocessor.

8.In what way interrupts are classified in 8085?

In 8085 the interrupts are classified as Hardware and Software interrupts.

9.examples of Software interrupts?

RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7.

10.EXAMPLES of Hardware interrupts? 

TRAP, RST7.5, RST6.5, RST5.5, INTR.

11.Which interrupt has the highest priority? 

TRAP has the highest priority.

12.Name 5 different addressing modes?

Immediate, Direct, Register, Register indirect, Implied addressing modes.

13.How many interrupts are there in 8085?

There are 12 interrupts in 8085.

14.What is clock frequency for 8085?

3 MHz is the maximum clock frequency for 8085.

15.In 8085 which is called as High order / Low order Register?

Flag is called as Low order register & Accumulator is called as High order Register.

16.Why crystal is a preferred clock source? 

Because of high stability, large Q (Quality Factor) & the frequency that doesn't drift with aging. Crystal is used as a clock source most of the times.

17.What does Quality factor mean?

The Quality factor is also defined, as Q. So it is a number, which reflects the lossness of a circuit. Higher the Q, the lower are the losses.

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1.what is the differnce between SCR and diode rectifier?ans: diode is a 2 terminal device, in scr gate controls the rectifing.SCR is used in High frequency applications but diode is low freuency devices, SCR can be in high temparatures but not diode. 

2.whatis intersymbol interferenceans:In telecommunication, intersymbol interference (ISI) means a form of distortion of a signal that causes the previously transmitted symbols to have an effect on the currently received symbol. This is usually an unwanted phenomenon as the previous symbols have similar effect as noise, thus making the communication less reliable. ISI is usually caused by echoes or non-linear frequency response of the channel. Ways to fight against intersymbol interference include adaptive equalization or error correcting codes (especially soft-decoding with Viterbi algorithm).

3.Distinguish between Angle modulation and Amplitude modulation.ans: In amplitude Modulation as the amplitude of given signal varies, the amplitude of carrier signal also varies in the same way.In angle modulation, the frequency or phase may vary according to the amplitude of given signal

4.What is Biasing?ans: biasing is a process of connecting dc voltage to a device by which we can select the operating point of the device. by biasing actually we select the operating point of the device.

5.What do you mean by ASCII, EBCDIC?ans:ASCII (American Standard Code for Information Interchange), is a character encoding based on the English alphabet.

EBCDIC (Extended Binary Coded Decimal Interchange Code) is an 8-bit character encoding used on IBM mainframe operating systems

6.What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?ans:3db implies 70%(o.7o7) of the power,i'e we r interested to consider the bandwidth range from peak to 70% b'coz uptp 70% its reliable.hence 3db is called as half power freq. 3db value is the mean square value which is 70% of the maximum value.

7.What is meant by pre-emphasis and de-emphasis?ans:Pre-emphasis

" Improving the signal to noise ratio by increasing the magnitude of higher frequency signals with respect to lower frequency signals"

De-emphasis" Improving the signal to noise ratio by decreasing the magnitude of higher frequency signals with respect to lower frequency signals"

8.What is sampling theorem?ans:It is defined as the sampling frequency should be greater than or equal to twice the sampling frequency then we can generate the original signal if the condition does not satisfy we get the signal in the distorted mannerit is given as ( fs >/ 2 fs)

9.What is Race-around problem? How can you rectify it?ans: A condition in logic network in which the difference in propagation times through two or more signal paths in the network can produce an erroneous output.in jk flip flop race around problem will occur when both the inputs are high. it can be prevented by using master slave jk flip flop

10.What is the basic difference between Latches and Flip flops?ans:latch works without clock signal,but works with a control signal and it is level triggered device.whereas flip flop is a 1 bit storage element and works with a clock signal.its a edge triggered device. normally latches are avoided and flip flops are preferred.

11. what is Barkhausen Criterion?ans:1./AB/=1,i.e. the magnitude of loop gain must be unity2.the total prase shift around the closed loop is zero or 360 degrees.

12.what are active and Passive Components?ans:ACTIVE COMPONENTS The components which produce the energy in the form of current or voltage are called as active components.Example:transistors etc,.

PASSIVE COMPONENTS The components which stores the energy in the form of current or voltage are called as passive components.example:inductors,resistors,capacitors etc

Technical Questions with Answers of Electronics And Telecommunication

1. What are the differences between voltage and current controlled devices?Ans-In any (electronic) device controlling parameter is current it is called current controlleddevice. eg bilpolar transistor- output current is a function of base current.In any (electronic) device controlling parameter is voltage it is called voltage controlled device.eg Field effect transistor- output current is a function of gate voltage.It depends on the inherent physical mechanism which defines the primary (independent)

controlling parameter.

2. What is the difference between Power Amplifier and Voltage Amplifier?Ans-Power amplifiers basically amplify both current and voltage (p=v*i). Voltage amplifiersonly amplify the voltage.In power amplifier feedback employed is current feedback and In voltage amplifier voltagefeedback is employed.

3. why the bjt is known as current controlled device and fet is known as voltage controlleddevice ?Ans- 1. In BJT because of the current the output will vary.2. Where as in FET by means of Voltage the output is varied.

4. What is the difference between DCS & PLC & SCADA ?Ans-PLC stands for Programmable Logic ControllerDCS for Data control SystemSCADA forSupervisory Control And Data Acquisition SCADA involves supervision by a user in most casesthe plant controller.Whereas PLC is the means by which he performs the function ofSCADA.DCS on the other hand stand only to control the system and not to log any datain theprocess of controlling.DCS controllers are faster than PLCs In DCS controller we can adjust thescan time DCS are costly more inputs and outputs are there for DCS and SCADA does nothave a dedicated controller. In a DCS system there is SCADA ystem already in it but for PLCsydtem addition all SCADA software must be provided.

5. What is the difference between Silicon Controlled Switch (SCS) and Gate Turn-off Switch(GTO)?Ans-scs is nothing but it is the silicon controlled switch as an SCR but gate turn off is that inwhich one of the turnoff method of SCR

6. What is the difference between emulator and simulator?Ans-Simulator: A software program impersonating a Hardware. Thus SIMULATING thescenarios faced in the original hardware.Emulator: A Hardware (with or without software) impersonating another Hardware. ThusELIMINATING the need for the original.

7. What is the difference between Circuit Switching and Packet

Switching? Ans-Circuitswitching is the transmission technology that has been used since the first communicationnetworks in the nineteenth century. In circuit switching, a caller must first establish aconnection to a callee before any communication is possible. During the connectionestablishment, resources are allocated between the caller and the callee.packet switching is a more recent technology than circuit switching which addresses adisadvantage of circuit switching: the need to allocate resources for a circuit, thus incurring linkcapacity wastes when no data flows on a circuit. Packet switching introduces the idea ofcutting data on a flow into packets which are transmitted over a network without anyresource being allocated.

8.the number of columns in a state table for a sequential circuit with m flip-flops and ninputs is.Ans-Its 2m+2n because.. If there are m flip-flops there should be 2m nodes. If there are ninputs then each node will have 2n.

9. Design a digital circuit which has one input two output and one select line input should be1000khz output should be 500khz and 250Khzselect line either 0 or 1if 0 select 250khzif 1 select 500khz

Ans-demux is the circuit which satisfies the given requirement if 0 is given to the selectline250khz o/p is provided else 500khz o/p is provided.

9- What are digital elctronic flip flops, State the different types of flip flop and their uses.Ans-Digital electronic flip flops are temporary single bit storage devices. Different types of flipflops are JK f/f RS f/f T F/F D f/f this flip flops are using as storage device delay purpose ascounter for toggled as shift register etc

10- What is the difference between latches and flip flop ?Ans-Latche is a bistable circuit which responds to change of logic level as they occur. It has noexternal inputs.Flip flop is a basic element of memory. It stores a single bit. It has a multiple

input.Latches are level sensitive devices where as Flipflops are edge sensitive device so it is said thatlatches are level triggered and flip flop is edge triggered.

11-What is the Tri State of a Signal?Ans-In digital ciruit the gate output can be only high or low. In highstate the output sourcecurrent at a minimum voltage greater than ~2.8V if load(fan out ) is proper. In low state it willsink current at max output voltage less than ~0.8V.Some times it is desirable to have a state output both not high or low. with neither sinking orsourcing (with high output impedance). This is called tristate. Tristate output cannot changeoutput condition of succeding logic gates unless tristate is disabled.

12- what is the main difference between 8085 and 8086 processors?Ans-8085 is a 8 bit microprocessor,having 16-bit address bus.8086 is a 16-bit microprocessorhaving 20-bit address bus.

13. What is a sequential circuit and What is a combinational circuit? Is there any differencebetween them? If yes what is it?Ans-Combinational circuit are those whose output depends only upon the present inputs butin sequential circuit the output depends upon both present and past inputs. that is thedifferenceCombinational circuit does not have any memory in the feedback path but the sequentialcircuit has memory in the feedback path.Ex of SEQ Circuit: Encoder Decoder etcEx of Comb Circuit; Flipflop

14. What is the difference between masking and non-masking?Ans-In 8085 processor TRAP is a non maskable interrupt.Whereas RST 7.5 6.5 5.5 intr are maskable interrupts.Maskable means this interrupts can be left without considering during the execution of theprogram.Non maskable depicts that it has to be taken into account during the execution of theprogram

15. What is difference between Fixed-Bias Circuit & Self-Bias Circuit?Ans-Fixed bias circuits get their bias voltages from independently designed reference voltagesources (or even something as simple as a voltage divider). Often is the case

that the bias maybe left for the end-user to give some control over the operation point of the circuit.Self biased circuits get their bias voltages from the circuit itself often in the form of a negativefeedback. This is very useful when a circuit is extremely sensitive to bias points and it becomesimpractical to provide external biases that are correct to very high accuracies. This can happenin high gain amplifiers with very high impedance output nodes such as a common sourceamplifier with an active load. The operation of the circuit dependson the bias of the activeload. It would therefore be desirable to sacrifice some of this gain by providing a negativefeedback from the output to the gate of the active load. This way you wont have to bias thecircuit yourself but will lose some of the gain of the circuit as a price.

16. What is meant by filter? What are the different types of filters?Ans-Filters are the components of a circuit which remove distortion or ripples.Types of filters :1. High pass filters2. Low pass filters3. Band pass filters

17. what is meant by virtual ground in the op amp ?Ans-Ideally the output of op-amp should be zero. So for this to happen the 2 inputs must besame. Hence one of the input is considered to be low or at ground potential. But this input isnot actually ground hence it is called as virtual ground.

18. What is meant by saying at what current is transistor biased?Ans-Bias current of a transistor is the preset DC current when no input voltage signal is appliedto it.

19. What is Race Around Condition in a JK FlipFlop?Ans-IN J-K FF , The clock time is higher than the output toggling time then for J=1 & K=1 , theoutput will be changed irrelavent of our input. This condition is known as "RACE AROUNDCONDITION"..

20. How to Convert Binary to Excess 3 Code and vice versa?Ans-A number i binary can be converted to excess-3 just by adding the binary equivalent of 3to the binary number.similarly a number in excess-3 can be converted to binary just by

subtracting the binary equivaent of 3 from the binary number.

21. How to convert Binary to Gray CodeAns-Take XOR of binary no. starting from right with the next bit. Add 0 as leftmost bit to getanswer eg. Â 111=7gray code 0 xor 1,1 xor 1, 1 xor 1 i.e. 100 ans.

22. What is the meaning of Tristate Signal in Electronics?Ans-Tristate device is 3 terminal device & it has three states. They are logic 0 logic 1 & highimpedance state or tristate. This device can be used as switch. For ON logic 0 or logic 1(depending on active low or active high appl) OFF as high independence state.

23. When a sample of germanium and silicon having same impurity density are kept at roomtemperature then Resistivity of silicon will be higher than that of germanium, Why?Ans-The answer is simple. Consider the PN diode for Ge 0.3eV is the breakdown voltage andin the case of Si its 0.7eV since the impurities are added in the same amount the bond due tothe other atoms of the Si makes it resistive compared to the Ge.. thats all!

24. Why gold is added to the p-n junction?Ans-To reflect heat. To reduce the recombination time.

25. Why are the 2 input terminals of an op-amp are called as inverting & non-invertingterminals?Ans-Because if we give input to one input means that will produce the same phase outputwhere as the other(Inverting) pin produce 180 degree phase shifted output.

26. What is the equivalent of negative logic AND gate?Ans-Negative logic of AND gate is NAND.

27. What are the main advantages of synchronous circuit?Ans-All the inputs are feed at the rising or falling end of the clock signal. This makes the circuitto perform task in sync. so that the functional integrity of the logic device is as expected.

28. How does a Signal differ from a WaveAns-Signal means information. Wave is something that carries the information from source todestination.

29. Why do we use two ground pins in the pin diagram of 8086?

Ans-There are basically two reasons for doing so one is to remove GROUND BOUNCE onemore reason is circuit complexity demands a large amount of current flowing through thecircuits and multiple grounds help in dissipating the accumulated heat so that device will besafe.

30. What is the difference between Power Amplifier and Voltage Amplifier?Ans-Power amplifiers basically amplify both current and voltage (p=v*i).Voltage amplifiers only amplify the voltage.

31. How to manufacture the CMOS inverter?Ans-It can be made by using pmos and cmos in series. Both gate are connected together andact as input. Source of pmos is connected to supply. drain of pmos is connected to drain ofnmosand it serves as output. source of nmos is grounded.

32. What are the advantages of using C band for satellite communication?Ans-Its frequency ranges from 12 to 18MHz

33. What is a BCD? What are its advantages and disadvantages? Why is an excess-3 code iscalled an unweighted code?Ans-BCD means Binary coded decimal its advantage is it can represent decimal numbers inthe form of binary value says (0000-0 to 1001-9).Binary codes are divided into weighted binary code and non weighted binary code Excess 3code is an example of non weighted codes since the position of each bits in excess 3 code doesnot have weights says like ones tens hundred in decimal and 2^0 2^1 2^2 in binary.

34. What is power electronics?Ans- Power electronics is the technology associated with high power which is more than 430v 3phase supply.Generally it is consider in industries for the efficient conversion control andconditioning of electric power by static means from its available input form into the desiredelectrical output form.

35. What are the differences between microprocessor and micro controller.Ans-The microprocessor is the integration of a number of useful functions into a single IC

package.These functions are: The ability to execute a stored set of instructions to carry out user definedtasks. The ability to be able to access external memory chips to both read and write data fromand to the memory.Basically a microcontroller is a device which integrates a number of the components of amicroprocessor system onto a single microchip.So a microcontroller combines onto the same microchip : The CPU core Memory (both ROMand RAM) Some parallel digital I/O Essentially a microcontroller is obtained by integrating thekey components of microprocessor RAM ROM and Digital I/O onto the same chip die. Modernmicrocontrollers also contain a wealth of other modules such as Serial I/O Timers and Analogueto Digital Converters.

36. What is function of ALE in 8085 microprocessor?Ans-AlE stands for the address latch enableit 's working is that it differentiate the address anddata bus in microprocessor.when it is high it select address bus .when it is low it select data bus.

37. Why we are using the bridge rectifier in most of the circuits instead of full wave rectifiereventhough the output of both are same?Ans-In bridge type (FWR) rectifiers center tapping transformer are not required so smalltransformers are used and we will get twice of the out put voltage that of the center tappedFWR.

38. What type of architecture is used in 8085 microprocessor?Ans- INTEL 8085 is a 8-bit microprocessor.It's based on Von-Neumann architecture in which the data and instructions are in the samememory space without any distinction between them.Data line: 8-bits--Can process 8-bits of data at a time.Address line: 16-bits--Can address upto 2^16(64KB) of address space.

39. What is Edison Effect?Ans-Edison Effect is also refferred as "Thermionic emission". Here the charge carriers flow froma charge-carrying surface due to vibrations caused by thermal energy.This phenomenon can be seen in the house-hold electrical bulb in which is a metal filament isheated by the thermal energy from electricity.

40. how to design a software IC using VHDL ?Ans-you can use software like altera write the required programme download to the chiphere is your software ic

41. What are semiconductor devices ?Ans-Semiconductor Devices is nothing but a device which conduct semi /partially conducting (semiconductor which conduction property lies between conductor and insulator)is termed assemiconductor device.

42. Why the input resistance of an ideal OP-AMP is infinite and output resistance is zero?secondly, how can we measure these resistances(input and output) in case of an ideal OPAMPandReal OP-AMP in the following conditions when1- load is not connected.2- load is connected.Ans- Ideal OP-AMP is a power ful concept.If one goes through the history of amplifying devices it becomes clear that less it loads theprevious stage better the output signal. ie. it is a trend toward higher and higher inputimpedances.Also it is better to maintain the signal level irrespective of the LOAD connected at the ouput.Lesser the output impedance less the signal amplitude reduction when load is connected. ie. itis a trend toward lower and lower output impedances.As ideal opamp is a concept by virtue it has zero output impedance and infinite inputimpedance and they are not physically measurable but has to be taken for granted for theuse in theoritical analysis.To measure input resistance of non ideal opamp connect a known source at the input andgive a signal (within Specifications) through a current meter of sufficient precision. Inputvoltage by current gives the input impedance.To measure input resistance of non ideal opamp connect a known source at the input andgive a signal (within Specifications) through a current meter of sufficient precision. Inputvoltage by current gives the input impedance.To measure output resistance of non ideal opamp connect a known source at the input suchthat the output does not saturate and connect a load (within Specifications ) through acurrent meter of sufficient precision and meaure the output voltage. Output

voltage bycurrent gives the output impedance.Can refer application notes by device manufacturer available in internet for moreprecise and practical solutions.

43. What is Pulse Width Modulation?Ans-Pulse width modulation is a modulation technique in which the width of the pulse isvaried in accordance with the message signal. Pulse width Modulation is abbreviated as PWM.PWM can be used to reduce the total amount of power delivered to a load without lossesnormally incurred when a power source is limited by resistive means. This is because theaverage power delivered is proportional to the modulation duty cycle. With a sufficiently highmodulation rate, passive electronic filters can be used to smooth the pulse train and recoveran average analog waveform.PWM is used in sound synthesis circuits.

44. How many type of resistor are there in diode?Ans-They are two types one is forward resistance1.Forward resistance2.Reverse resistance1.Forward resistance-This is the resistance offered in forward bias condition of the diode. It iscalculated by with the help of graph for voltage and current characteristic.2.Reverse resistance-This resistance is offered in the reverse bias condition of the diode. It is alsocalculated by the same method.

45. Why the shape of OP-AMP is triangular not other shape?Ans-The Triangular shape symbolizes that it works for continous signals and hence forth it is ananalog device. ex: OpampIf it is square then it is digital device. ex: MultiplexerIf the shape is both triangular and square then it is mixed signal device. ex: ADC DAC

46. What is Interfacing?Ans-The peripheral (simple input/output devices ) connected with computer to perform tasksis known as interfacing.

47 How microprocessor works without internal memory?Ans-microprocessor works without internal memory because it consists of adreess data andcontrol buses with some registers to process the task given to processor through the external

memory.

48. What is a sequential circuit and What is a combinational circuit?Is there any differencebetween them? If yes what is it?Ans-Combinational circuit are those whose output depends only upon the present inputs butin sequential circuit the output depends upon both present and past inputs. that is thedifference.

49. What are digital elctronic flip flops, State the different types of flip flop and their uses.Ans-digital electronic flip flops are temporary single bit storage devices.different types of flipflops are JK f/f RS f/f T F/F D f/f this flip flops are using as storage device delay purpose ascounter for toggled as shift register etc

50. What CMOS Transistor?Ans-CMOS-->>Complementary Metal Oxide SemiconductorComplementary metal–oxide–semiconductor (CMOS) is a major class of integrated circuits.CMOS technology is used in chips such as microprocessors microcontrollers static RAM and otherdigital logic circuits. CMOS technology is also used for a wide variety of analog circuits such asimage sensors data converters and highly integrated transceivers for many types ofcommunication.CMOS is also sometimes explained as complementary-symmetry metal–oxide–semiconductor.The words "complementary-symmetry" refer to the fact that the typical digital design stylewith CMOS uses complementary and symmetrical pairs of p-type and n-type MOSFETs forlogic functions.Two important characteristics of CMOS devices are high noise immunity and low static powersupply drain. Significant power is only drawn when its transistors are switching between on andoff states; consequently CMOS devices do not produce as much heat as other forms of logicsuch as TTL (transistor-transistor logic). CMOS also allows a high density of logic functions on achip.The triple compound "metal–oxide–semiconductor" is a reference to the nature of the physicalstructure of early (and interestingly now the very latest) field-effect transistors having a metal

gate electrode placed on top of an oxide insulator which in turn is on top of a semiconductormaterial. Instead of metal current gate electrodes (including those up to the 65 nanometertechnology node) are almost always made from a different material polysilicon but the termsMOS and CMOS nevertheless continue to be used for the modern descendants of the originalprocess. (See also MOSFET.) Metal gates have made a comeback with the advent of high-kdielectric materials in the CMOS transistor as announced by IBM and Intel for the 45nanometer node and beyond

51 . What is Virtual Grounding?Ans-Virtual grounding is the shorting of the inverting and the non-inverting terminals of theop-amp.The i/p resistance of opamp is v high. thus the base currents are v less approx 0. thus nocurrent flows thru i/p resistance. thus we can say that both the NI and INV terminals of opampare virtually shorted. i.e the voltage across both terminals is same. thus if NOW one terminal isgrounded due to virtual short other terminal also will be grounded.

52. Why the input impedance of OP-Amp is so high?Ans-In OPAMP we have 4 stages 1st stage i.e the input stage is a dual i/p balanced o/p opampwhose i/p resistance is v high. and if we use FET in case of BJT for 1st stage diffamp then i/presistance will be v high in M ohms.

53. what is meant by virtual ground in the op amp ?Ans-The op amp connected in a negative feedback configuration that is the o/p connected tothe inverting terminal tried to produce the same voltage at the inverting node as we appliedto the non-inverting terminal no matter whatever be the o/p. This happens because theopamp has a very high differential gain. so only way to not to clip or saturate the o/p in eitherpositive or negative side is to make their both i/ps at the same potential. so when you applythe i/p to the inverting terminal and you connect the feedback to the inverting node and yournon-inverting terminal is grounded then op amp tries to force the inverting node at theground potential and whatever the difference between these two nodes are amplified.

54. Which one is faster between NAND-SR FF and NOR-SR FF?Ans-well both deals with same principle.but i think NAND-SR FF is faster than NOR-SR FF

55. Cost of storing a bit is minimum in1. Cache 2. Register3. RAM 4. Magnetic tapeAns-Magnetic Tape

56. How many characters per sec (7 bits + 1 parity ) can be transmitted over a 2400 bps lineif the transfer is synchronous (1 start and 1 stop bit)?1. 300 2. 2403. 250 4. 275Ans- 2400/(7+1+2) 240

57. What does CE mean..U will see it on almost every chip(IC)..Ans-The CE mark is a mandatory European marking for certain product groups to indicateconformity with the essential health and safety requirements set out in European Directives.The letters 'CE' are an abbreviation of Conformité Européenne,French for European conformity. The CE mark must be affixed to a product if it falls under thescope of the approx. 20 so called 'New Approach' Directives. Without the CE marking, andthus without complying with the provisions of the Directives, the product may not be placed inthe market or put into service in the fifteen member states of the European Union andNorway, Iceland and Liechtenstein. However, if the product meets the provisions of theapplicable European Directives, and the CE mark is affixed to a product, these countries maynot prohibit, restrict or impede the placing in the market or putting into service of the product.Thus, CE marking can be regarded as the products trade passport for Europe. The CE mark isnot a quality-mark. First, it refers to the safety rather than to the quality of a product. Second,most quality markings are voluntary opposite to the CE marking, which is mandatory for theproducts it applies to. CE indicates conformity with mandatory European safety requirements.European conformity is certified by following clear and understandable procedures, the socalled‘conformity assessment procedures’

58. What is the difference between PLC and DCS?

Ans-PLC means Programmable Logic Controller, which can be used to control one particluarcontrol system such as a boiler or a injection system.but DCS is Distributed control syetem, which is used to monitor and control the total processplant. in DCS we have no of controllers connected to a single monitoring system.

59. why the feeding frequency to a microprocessor s twice the operating frequency.Ans-since 8085 microprocessor operating frequency 5 mega hz but operating frequency is 10mega hz because crystal effect in processor

60. Do we have any negative frequency?Ans-no it can't be negative because freguency is simply the reciprocal of time and time can'tbe negative.We use negative frequencies in our calculations just for easieness but remember at last weneglect it also

61. what is angle and amplitude modulation? what is noise in modulation?Ans- modulation means change. to send a message of low frequency to a far distance we usea carrier of high frequency to carry the message. while transfering we change someparameters of carriers for faithful tranformation of message signal. if the amplitude of thecarrier is varied in accordance with frequency of message signal then it is called amplitudemodulation. if either phase or frequency is changed in accordance with the frequency ofmessage signal then it is called angle modulation.noise is an unwanted signal which enter in signal while transfering a signal and makes thesignal distorted.

62. what is selective flooding?Ans- Selective Flooding is a method to compute the Qos of the system

63. what is fixed bias with and without decoupling capacitorAns- with ta decoupling capacitor u cannt get o/p bcz it blocks the DC and allows only ACok.... is u dont us it it give the o/p but it's DC only so no use to hav a DC voltage in O/P

64. what is the main application of scr in electronic field as well as in software field?Ans- SCR is a rectifier we use this in power handling applications .

By varying on time and off time of the scr i.e by giving the pulse to its gate we can vary theaverage output power from the main power supply to the required device .software partwe can use micro controller and write a programme so that to generate required pulses tocontrol the SCR.

65. What is Biasing?Ans- Biasing is process of applying potential across any electronic equipment in order to makeit operate as we require.