One Liner about Basic Electronics for RRB JE

In this article basic one liners about basic electronics will be discussed which are frequently asked in RRB JE exams.
Electronics is a branch of engineering in which we study behaviour,  movement and uses of electrons or charge carriers in a semiconductor.

1. Semiconductors have four electrons in external orbit examples are Silicon (Atomic number 14) and Germanium (atomic number 32). 

The process of mixing impurities is called Dopping. 

When same wafer of semiconductor is doped with different impurities then charge carriers movement from high concentration to lower concentration region is called diffusion.

The movement of charge carriers from one region to another region because of applied electric potential is called drift.

2. Pure Semiconductor is called intrinsic Semiconductor and when doped with impurities it is called as extrinsic Semiconductor.

3. Pentavalent impurities like Boron, aluminium,  thallium and indium produces N type Semiconductor after dopping.

4. Trivalent impurities like Arsenic,  antimony, bismuth and phosphorus produces P type Semiconductor after dopping.

5. Barrier potential or knee voltage of Silicon and Germanium are 0.7 V and 0.3 V respectively.

6. Forbidden energy gap of Silicon and Germanium are 1.12 eV and 0.72 eV respectively.

7. Diode is a non linear semiconductor device which is used as one way switch.

8. Zenor Diode is special purpose Diode operates in reverse breakdown mode and used in voltage regulation.

9. Light emitting Diode (LED) operates in forward biased and used in LED tv, indicators, and torches.

10. Optocoupler is a combination of LED and photo Diode which is used in automatic doors and wireless signal transmission.

11. Light amplification by stimulated emission of radiation (LASER) is a Diode which operates in forward bias and produces coherent light. LASER is used in communication,  medical , industrial applications and defence equipments.

12. Varactor Diode is a reverse biased Diode which is used in TV and radio receivers for tunning purpose. 

13. Diode is mostly used in Rectifiers to convert ac into dc.

14. In half Bridge rectifier one diode is used because of which only one cycle of AC is obtained at the output. Frequency of output and input remains same. For example if we give 50 Hz voltage or current in input of half wave rectifier then output Waveform frequency will also be 50 Hz.

15. Half wave rectifier has ripple Factor 1.21 and efficiency 40.6 %.

16. Full wave bridge rectifier useses four diodes to convert ac waveform into dc. Frequency of output waveform get doubled. For example if 50 hz waveform is given in input then output waveform frequency will be 100 Hz.

17. Full wave rectifier has ripple factor 0.482 and efficiency 81.2 %. 

18. 1N4007 is a pn diode normally used in rectifier and has reverse breakdown voltage of 1000 Volt.

19. OA 79, 1N914 and 1N4148 are signal diode. 

20. Schottky diode is special purpose diode with almost zero reverse recovery time and used in switch mode power supplies, inverters and converters because of its high switching speed  (above 300 MHz) .

21. 1N5817, 1N5818, and SR360 are schottky diode.

22. 1N5408 is a Silicon diode or power diode which is used in high power applications like Rectifiers,  Voltage doublers and battery charger circuits.

23. Bipolar junction transistor (BJT) is a current controlled device in which switching or amplification is controlled by applying current at input of base terminal.

24. Transistor can operate in four region in which active region is used for amplification, saturation and cut off region are used for switching purpose. Inverted mode is not used normally.

25. Transistor has three layer emitter, base and collector in which emitter is highly doped, base is lightly doped and collector is moderately doped.

26. Field effect transistor (FET) is a voltage controlled device. In FET current passing through it is controlled by gate input voltage.

27. MOSFET full form is Metal oxide Semiconductor field effect transistor. It is used in high frequency switching circuits.

28. SCR full form is Silicon controlled rectifier. SCR has four layers, three junctions and three terminals anode, cathode & gate.

29. In SCR latching current is the value of minimum anode current which is required to turn on a SCR or thyristor and holding current is the value of minimum anode current which can flow through a SCR or thyristor in ON state.

30. unijunction transistor (UJT) is used to trigger a SCR by providing it a gate pulse.

31. Thyristor is a combination of THYRatron tube and transISTOR. It is a solid state device like transistor and can deal with large amounts of power like thyratron tube. Thyristor is basically a family which consists SCR, TRIAC, DIAC, Power diode, power transistor,  power mosfet, GTO and IGBT like members in the family.

32. Triac is a three terminals bilateral semiconductor switching device which can control alternating current in a load. 

33. Diac two teeminal, three layer bidirectional device which is used for Triac triggering. Diac exhibits negative resistance property means current through the device increases with decrease value of applied voltage.

34. GTO full form is gate turn off thyristor which are used in electric Locomotives Traction converter circuits for switching of high power voltages. 

35. IGBT full form is insulated gate bipolar transistor which are a replacement of GTO in electric Locomotives Traction converter circuits because of its high power handling capability.

36. Amplifier is a device which increases the current,  voltage or power of an input signal with the help of transistor by producing additional power from a separate source of power supply.

37. In Class A amplifier transistor operates in active region at all times which means collector current flows for 360° of the AC cycle. Class A amplifier efficiency is 25 % and has very less distortion. These are used in voltage amplifiers example  preamplifier in audio amplifiers.

38. In Class B amplifiers collector current flows for only half cycle (180°) this is why transistor Q point lies at cut off. These are used with push pull arrangements with maximum efficiency pf 78.5 %. These amplifiers have small to moderate distortion and uses in power amplifiers example public address system audio amplifiers which are used for announcements in railway stations.

39. In Class C amplifiers collector current flows for less than 180 ° of the AC cycle. Maximum efficiency is near to 100 % but has large distortion. These amplifiers are used in RF power amplifiers examples satellite communications , mobile communications etc.

40. An Oscillator is an electronic device that generates sinusoidal oscillations of desired frequency.

41. Positive feedback Circuit is used in oscillators to obtain sustained oscillations at output. Positive feedback Circuit converts feedback voltage in phase with the input voltage. We can say feedback voltage and input voltage have 0° phase difference.

42. Wien Bridge Oscillator produces 1 MHz to 5 MHz frequency oscillations and used in commercial audio generators and signal generators in laboratories.

43. Hartley Oscillator is used in radio receivers of television.

44. Crystal Oscillators are used in wristwatches, radios, computers and mobiles. These Oscillators provide most stable and accurate oscillations upto 10 MHz frequency.

45. Cyclo Converter is used to convert frequency of input AC voltage. By changing frequency speed of Induction motor can be changed. 

46. SCR is used for speed control of dc motor.

47. IGBT are used for Controlling voltage to control the speed of Induction motors.

48. Operational Amplifier is a multistage amplifier and consists of a differential amplifier, a high CE amplifier stage and Class B push pull emitter follower.

49. Operational amplifier can perform mathematical operations as addition, subtraction,  integration and differentiation.

50. Operational amplifiers are used in Rectifiers, clippers, clampers, comparators, Buffer circuits, signal generators etc.

Author:- Amarjeet Singh Jamwal authored articles on Basic Electronics EngineeringElectric Traction, and Electronics Practical for INFO4EEE Website

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