Electronics and communication engineering core interview questions.

[no signal]

MY 20

1: 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 ?


ATB all

will add more..:razz:

[diablorulez]

Q 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 micro
A.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.

[diablorulez]

1. What is meant by D-FF?
2. What is the basic difference between Latches and Flip flops?
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?
8. What do you mean by an ideal voltage source?
9. What do you mean by zener breakdown and avalanche breakdown?
10. What are the different types of filters?
11. What is the need of filtering ideal response of filters and actual response of filters?
12. What is sampling theorem?
13. What is impulse response?
14. Explain the advantages and disadvantages of FIR filters compared to IIR counterparts.
15. What is CMRR? Explain briefly.
16. What do you mean by half-duplex and full-duplex communication? Explain briefly.
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?
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?
26. What do you mean by ASCII, EBCDIC?

[Surfacer]

answers to some in blue

Originally Posted by diablorulez

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?

[godsforgottench]

Me in red. Verify the answers and plz revert back....thanks

Originally Posted by diablorulez

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?

[crazy_about_cat]

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 FB
Cut-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 processors
MC have inbuilt memory and IO ports
to 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.

Cheers,
Vivek

[sir roy keane]

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.

[sir roy keane]

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.

[diablorulez]

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 interference
ans: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 unity
2.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

[forgiven]

hey grt work diablo...thx for ur elec Q&A.....will help a lot..
keep quizzing!!......