Electronics,ECE Interview Questions

Electronics,ECE Interview Questions
1. Expand ECE.
Electronics & Communication Engineering.
2. What is Electronic?
3. What is communication?
4. Different types of communications? Explain.
Analog and digital communication.
5. What is engineering?
The application of science to the needs of humanity and a profession in which a knowledge of the mathematical and natural sciences gained by study, experience, and practice is applied with judgment to develop ways to use economically the materials and forces of nature for the benefit of mankind.
6. Difference between electronic and electrical.
Electronics work on DC and with a voltage range of -48vDC to +48vDC. If the electronic device is plugged into a standard wall outlet, there will be a transformer inside which will convert the AC voltage you are supplying to the required DC voltage needed by the device. Examples: Computer, radio, T.V, etc...
Electric devices use line voltage (120vAC, 240vAC, etc...). Electric devices can also be designed to operate on DC sources, but will be at DC voltages above 48v. Examples: are incandescent lights, heaters, fridge, stove, etc...
7. What is sampling?
8. State sampling theorem.
9. What is cut-off frequency?
10. What is pass band?
11. What is stop band?
12. Difference between mobile and a cell phone.
There is no difference, just language use, which differs from country to country, so in Britain it is called a mobile, and in USA and South Africa and other places a cell phone.
Even in Europe the name differs. The Germans call it a "handy", which in English has completely another meaning as an adjective, meaning useful.
In Italy it is called a telofonino or "little phone".
This difference in British and American English is also evident in many other things we use every day, like lifts and elevators, nappies and diapers, pickups and trucks. The list goes on and on, any student of English has to decide which he or she will use, as the default setting.
13. Explain RF?
14. What is modulation? And where it is utilized?
Radio communication superimposes this information bearing signal onto a carrier signal.
15. What is demodulation?
16. Name the modulation techniques.
17. Explain AM and FM.
18. Where do we use AM and FM?
19. How does a mobile work?
When you talk into a mobile telephone it converts the sound of your voice to radiofrequency energy (radio waves). The radio waves are transmitted through the air to a nearby base station. The base station then sends the call through the telephone network until it reaches the person you are calling. When you receive a call on your mobile phone the message travels through the telephone network until it reaches a base station near to you. The base station sends out radio waves, which are detected by your telephone and converted back to speech. Depending on the equipment and the operator, the frequency that each operator utilises is 900MHz, 1800MHz or 2100MHz.
The mobile phone network operates on the basis of a series of cells. Each cell requires a radio base station to enable it to function.
There are three types of base station and each has a particular purpose:
1. The Macrocell is the largest type and provides the main coverage for mobile phone networks.
2. The Microcell is used to improve capacity in areas where demand to make calls is high, such as shopping centres.
3. The Picocell only has a range of a few hundred metres and may be used to boost weak signals within large buildings.
Each base station can only cope with a certain number of calls at any one time. So if demand exceeds the capacity of a base station an additional base station is needed.
20. What is a base station?
21. How many satellites are required to cover the earth?
22. What is a repeater?
23. What is attenuation?
Attenuation is the reduction in amplitude and intensity of a signal. Signals may attenuate exponentially by transmission through a medium, or by increments calculated in electronic circuitry or set by variable controls. Attenuation is an important property in telecommunications and ultrasound applications because of its importance in determining signal strength as a function of distance. Attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc) and is represented by the attenuation coefficient of the medium in question.
24. What is multiplexing?
Multiplexing (known as muxing) is a term used to refer to a process where multiple analog message signals or digital data streams are combined into one signal over a shared medium. The aim is to share an expensive resource. For example, in telecommunications, several phone calls may be transferred using one wire.
25. What is CDMA, TDMA, FDMA?
26. Difference between CDMA and GSM.
These are the two different means of mobile communication being presently used worldwide. The basic difference lies in the Multiplexing method used in the aerial communication i.e. from Mobile Tower to your mobile and vice versa.
CDMA uses Code Division Multiple Access as the name itself indicates, for example you are in a hall occupied with number of people speaking different language. You will find that the one language you know will be heard by you and the others will be treated like noise. In the same manner each CDMA mobile communication takes place with a "code" communicating between them and the other end if one is knowing that code then only it can listen to the data being transmitted i.e. the communication is in the coded form.
On the other hand GSM (Global System for Mobile Communications) uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. TDMA works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way, a single frequency can support multiple, simultaneous data channels.
27. What is an Amplifier?
28. What is Barkhausen criteria?
“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product of the transfer gain of the amplifier and the magnitude of the feedback factor of the feedback network ( the magnitude of the loop gain ) are less than unity”.
The condition of unity loop gain -Aβ = 1 is called the Barkhausen criterion. This condition implies that

= 1and that the phase of - Aβ is zero.
29. Explain Full duplex and half duplex.
Full duplex refers to the transmission of data in two directions simultaneously. For example, a telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplex device because only one party can transmit at a time.
Most modems have a switch that lets you choose between full-duplex and half-duplex modes. The choice depends on which communications program you are running.
In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party. This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.
30. What is a feedback? And explain different types of feedback.
Types of feedback:
Bipolar feedback: which can either increase or decrease output.
31. Advantages of negative feedback over positive feedback.
32. Example for negative feedback and positive feedback.
Example for –ve feedback is ---Amplifiers
And for +ve feedback is – Oscillators
33. What is Oscillator?
34. What is a transducer and transponder?
A transducer is a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaic that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer.
In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) has the following meanings:
* An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator).
* An automatic device that transmits a predetermined message in response to a predefined received signal.
* A receiver-transmitter that will generate a reply signal upon proper electronic interrogation.
A communications satellite’s channels are called transponders, because each is a separate transceiver or repeater.
35. What is an Integrated Circuit?
36. What is crosstalk?
37. What is a rectifier?
A rectifier changes alternating current into direct current. This process is called rectification. The three main types of rectifier are the half-wave, full-wave, and bridge. A rectifier is the opposite of an inverter, which changes direct current into alternating current.
HWR- The simplest type is the half-wave rectifier, which can be made with just one diode. When the voltage of the alternating current is positive, the diode becomes forward-biased and current flows through it. When the voltage is negative, the diode is reverse-biased and the current stops. The result is a clipped copy of the alternating current waveform with only positive voltage, and an average voltage that is one third of the peak input voltage. This pulsating direct current is adequate for some components, but others require a more steady current. This requires a full-wave rectifier that can convert both parts of the cycle to positive voltage.
FWR- The full-wave rectifier is essentially two half-wave rectifiers, and can be made with two diodes and an earthed centre tap on the transformer. The positive voltage half of the cycle flows through one diode, and the negative half flows through the other. The centre tap allows the circuit to be completed because current cannot flow through the other diode. The result is still a pulsating direct current but with just over half the input peak voltage, and double the frequency.
38. What is resistor?
39. What is capacitor?
A capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate.
Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters.
Capacitors are occasionally referred to as condensers. This term is considered archaic in English, but most other languages use a cognate of condenser to refer to a capacitor.
40. What is inductor?
41. What is conductor?
42. What is a semi conductor?
43. What is diode?
44. What is transistor?
45. What is op-amp?


bindu said...

excellent.....it's really useful..pls add some more interview questions...the concepts you have provided are really awesum ..good work keep it up

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