# Basic Electronics Lab Viva Questions

Experiment wise viva questions Basic Electronics Lab

PN-Junction Diode:

1. What is a diode?
2. What are the applications of diode?
3. Draw the symbol of PN junction diode and mark anode and cathode.
4. Define threshold voltage or cut in voltage of a diode.
5. define dynamic and static resistances of a diode.
6. Cut-in voltage of Si diode is…………………
7. Cut-in voltage of Ge diode is…………………
8. Draw the VI characteristics of PN junction diode.
9. What is forward bias of a junction diode? Explain with circuit diagram.
10. What is reverse bias of a junction diode? Explain with circuit diagram.
11. Define space charge or Depleted region of a diode?
12. Explain the working operation of a junction diode in forward and reverse bias.
13. p type material means………….. Give some examples of N-type materials
14. n type material means…………Give some examples of P-type materials
15. Ideal diode acts as short circuit under forward bias. Or draw the equivalent circuit of ideal diode in forward bias.
16. Ideal diode acts as open circuit under reverse bias. Or draw the equivalent circuit of ideal diode in reverse bias.
17. Draw the equivalent circuit of practical diode in forward bias and reverse bias.
18. What are the differences between avalanche and Zener break down.
19. What are intrinsic and extrinsic impurities?
20. Differentiate a conductor, semiconductor and dielectric material.
21. Write the diode current equation.

Zener Diode:

1. What is Zener diode? Define how it is different from ordinary PN diode.
2. What are the applications of Zener diode?
3. Draw the symbol of Zener diode and mark anode and cathode.
4. Define Zener breakdown.
5. What is the Zener breakdown voltage value———–.
6. How Zener diode is acting as a voltage regulator?
7. What is the cut-in voltage of a Zener diode————.
8. Draw the equivalent circuit of Zener diode?
9. Zener diode operates in reverse bias? Why?
10. Explain avalanche multiplication in detail.
11. Explain Zener multiplication in detail.
12. Give two differences between avalanche and Zener multiplication.

Half Wave rectifier and Full wave Rectifier (same questions are valid for FWR)

1. What is a rectifier? How diode is used as a rectifier?
2. Define ripple factor?
3. What is the need for filter at the output of a rectifier?
4. What is percentage of regulation?
5. Give the ripple factor values for HWR and FWR (read comparison table between HWR and FWR).
6. What is the efficiency of HWR and FWR? Give values.
7. What are the advantages of FWR over HWR?
8. What are the disadvantages of HWR?
9. What are the drawbacks of FWR?
10. Define PIV of a diode.
11. PIV of HWR and FWR are………..
12. why we need rectifiers?
13. where we use rectifiers ?
14. what are the differences between rectifier and converter?

CE/CB characteristics:

1. Draw the symbol of transistor.
2. Draw pnp and npn transistor symbols.
3. What are three configurations of a BJT?
4. Draw the circuits of CE, CB and CC configurations.
5. What is CE or Grounded Emitter configuration?
6. What is CB or Grounded Base configuration?
7. What is CC or Grounded Collector configuration?
8. What are input and output characteristics of BJT?
9. Draw input and output characteristics of CE configuration.
10. Draw input and output characteristics of CB configuration.
11. What are the applications of CE and CB transistors?
12. Comparison table of CE, CB and CC configurations in terms of input resistance, output resistance, voltage gain, current gain and applications.
13. What are the three terminals of a transistor?
14. Define doping levels of emitter, base and collector.
15. Define early effect in CB transistor.
16. The majority carriers in pnp transistor are………..
17. The majority carriers in npn transistor are………..
18. Why BJT is called as bipolar device?
19. Is BJT a uni polar or bipolar device?
20. What are the applications of transistors?
21. what is the phase difference between input and output waveforms of CE transistor( ans: 180o)
22. What is the phase difference between input and output waveforms of CB transistor ( ans: 0o or 360o).
23. Why NPN transistor is preferred over PNP transistor?
24. Why CE is preferred over other combinations in voltage amplifiers?
25. Define saturation, cutoff, active regions of a transistor?
26. What is cutoff region of operation of a transistor?
27. Read about comparison tables of Si, Ge transistors for active cutoff and cutin and saturation voltages.

JFET:

1. What is FET or JFET?
2. What are the differences between BJT and FET?
3. Why BJT is called as Current controlled device?
4. Why FET is called as Voltage controlled device?
5. Draw the symbol of FET?
6. Symbols of N-channel and p channel FETs.
7. Differences between N- channel and P- channel FET’s?
8. Draw the input or output characteristics of JFET?
9. What are the meanings of source drain and gate?
10. What are the applications of FET?
11. What are the advantages of FET over BJT?
12. Draw h-parameter model of a BJT in CE/CB configurations?
13. Define pinchoff voltage of a FET?
14. Explain about linear saturation and breakdown regions of CE/CB output characteristics?
15. Explain about linear saturation and breakdown regions from drain or output characteristics of JFET
16. Define 4 h-parameters of BJT in CE configuration?
17. Draw the equivalent circuit of FET?
18. define µ, g , rd in FET? what is the relation between those three parameters?
19. define trans conductance and drain resistance of FET?
20. The input resistance of a JFET is very high in Mega ohms.
21. Working of JFET.
22. Applications of JFET.

Operational Amplifier:

1. What is Operational Amplifier?
2. What are the ideal characteristics of Op-amp?
3. What are the applications of op-amp?
4. What is inverting amplifier?
5. What is non inverting amplifier?
6. What is meant by open loop and closed loop op-amp?
7. Identify the feedback resistor in inverting and non inverting amplifiers (ans:Rf).
8. What are the advantages of op-amp over feedback amplifiers?
9. Define slew rate?
10. Draw circuits of integrator and differentiator using op-amp
11. Draw adder and subtractor circuits using op-amp.
12. What is virtual ground in op-amp circuits?
13. What is open loop gain of an ideal op amp?

Oscillators:

RC Phase Shift Oscillator:

1. Mention the two conditions required for oscillations in RC phase shift oscillator?
2. Give the formula for frequency of oscillations in RC phase shift oscillator?
3. The phase produced by a single RC network is RC phase shift oscillator?
4. RC phase shift oscillator uses positive feedback or negative feedback?
5. The phase produced by basic amplifier circuit in RC phase shift oscillator is?
6. What is the difference between damped oscillations and un damped oscillations?
7. What are the applications of RC phase shift oscillator?
8. How many resistors and capacitors are used in RC phase shift feedback network?
9. How the Barkhausen’s criterion is satisfied in RC phase shift oscillator
10. Mention the basic reason for any oscillations?
11. What is meant by Barkhausen’s criterion?
12. Audio frequency range is————
13. RC phase shift oscillator is ——–
14. Oscillator is a circuit operates on internal input power supply yes or no?
15. Define an oscillator?
16. Oscillator did not take any external input yes or no?
17. Type of feedback used in oscillators is——-
19. Show that single RC section provides a phase shift of 60 degrees.
20. Positive feedback causes instability yes or no?
21. In oscillators loop gain must be————–
22. In oscillators the overall phase shift produced by the circuit is————
23. Feedback gain 𝛽 must be less than———–

COLPITTS AND HARTLEY’S OSCILLATORS:

1. What are the advantages of hartley’s and colpitts oscillators over RC phase shift oscillator?
2. Applications of Colpitts and Hartleys oscillators are—–.
3. Colpitts oscr uses ———- in its feedback network.
4. Hartleys oscr uses ———–in its feedback network.
5. Define mutual inductance—–
6. colpitts and hartleys ocsillators are used at ———— frequencies.
7. Give the formula for frequency of oscillations in Colpitts oscillator.
8. Give the formula for frequency of oscillations in Hartley’s oscillator?

SINGLE STAGE CE AMPLIFIER:

1. What is the phase difference between input and output waveforms of a CE amplifier?
2. What type of biasing is used in the given circuit?
3. What is the effect of emitter bypass capacitor on frequency response of a CE amplifier?
4. What is the effect or importance of coupling capacitor?
5. Why source resistance Rs is used in the input side?
6. What are the different regions of operation of a BJT?
7. The phase difference of input and output in CB amplifier?
8. CE amplifier is voltage or current amplifier?
9. Draw the equivalent h-parameter model of a CE amplifier?
10. Why NPN transistor is preferred over PNP transistor?
11. What is the effect of bypass capacitor over stability of the CE amplifier?
12. The CE amplifier is in voltage divider bias or in fixed bias configuration?
13. The values of hfe,hie,hoe and hre in CE configuration are—————-.
14. hfe,hie,hoe and hre are called as——————–.
16. What are the practical applications of single stage CE amplifier?
17. How do you know the amplifier is single stage CE amplifier?
18. Why this circuit is called RC coupled amplifier?
19. What is the operating point in CE amplifier from the design specifications?
20. Quiescent conditions means——–
21. D.C conditions are for———
22. What is the relationship between collector current and base current?
23. Does β and hfe are one and the same?
24. Why coupling capacitor Cb is connected in reverse (-,+) at the input side and Cc is connected in forward(+,-) at the output side?
25. How do u know a transistor is working in cut off region?
26. Write VBE(active),VBE(sat),VBE(cutoff) values of a Si and Ge transistors
27. Transistor meaning is———
28. Define frequency response of a CE amplifier?
29. Define voltage gain of a CE amplifier?
30. Units of gain as a ratio are———-
31. Units of gain in logarithim is———
32. Magnitude response and frequency response are one and the same say yes or no?
33. Define bandwidth?
34. What are 3 dB frequencies?
35. Define cutoff frequencies?
36. BW is approximately equal to fH justify?
37. Gain is constant in————-
38. Semi logarithmic graph is linear or non linear graph?
39. Stability factor is a function of—–
40. In the circuit R1 and R2 are used for——–
41. The feedback type that Re and Ce introduces in the circuit is———–(Ans: negative feedback).
42. Negative feedback increases stability yes or no(Ans:yes).
43. CB amplifier provides more band width than CE amplifier justify?

ALL THE BEST

Prepared by   P.Lakshmi Prasanna

## Author: Lakshmi Prasanna Ponnala

Completed M.Tech in Digital Electronics and Communication Systems.

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