EDC Question Bank

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ELECTRONIC DEVICES AND CIRCUITS

Question Bank

UNIT 1

PART A 1. Draw the VI characteristics of a PN Junction diode.

2. A Ge diode has a saturation current of 10 μA at 300°K. Find the

saturation current at 400°K.

3. Define Barrier Potential.

4. State the applications of PN junction diode.

5. Define the cutin voltage and peak inverse voltage of a PN

Junction diode.

6. What is meant by doping in semiconductors? What is the need

for doping?

7. Give the diode current equation.

8. Define cutin voltage.

9. What is meant by depletion region?

10. Define the transition capacitance of a diode.


PART – B

11. (a) With a neat diagram, explain the working of a PN Junction diode in

forward bias and in reverse bias.

Or

(b) (i) Explain the switching characteristics of PN Junction diode (10)

(ii) Discuss the effect of doping on depletion region (6)

12. (a) Explain the working of PN junction diode with forward and reverse

characteristics.

Or

(b) Write in detail on Transition and Diffusion capacitance.

13. (i) Describe the constructional details, characteristics and working

principle of Depletion MOSFET. (12)

(ii) Write a note on FET as a variable resistor. (4)

14. (a) Explain the working of a PN junction diode under various biasing

conditions using the relevant circuit sketch.

Or

(b) (i) Explain how a PN junction is formed? (8)

(ii) Write a note on diode capacitors. (8)


15. (a) With the volt-ampere characteristics, explain the working principle

of the diode and also explain the static dynamic resistance of the diodes?

(16)

0r

(b) Write a detailed note on:

(i) Diode switching times. (6)

(ii) applications of diodes. (4)

(iii) capacitance of diodes . (6)

UNIT 2

PART A

1.For a npn transistor IE=12mA and β=140. Determine the value of

IB and IC.

2. A transistor connected in common base configuration has a

_________ input resistance and a ________ output resistance.

3. What is emitter follower? State the applications of the same.

4. Which transistor configuration is mostly used as an amplifier,

why?

5. In a bipolar transistor, which region is wider and which is

thinner? Why?

6. Draw the hybrid model of a CE transistor.

7. Give the current gain expression for a common emitter

transistor configuration.

8. What are the tools used for small signal analysis of BJT?


9. What are power transistors?

10. Which of the BJT configuration is suitable for impedance

matching applications? Why?

PART – B

11. (a) The hybrid parameters for a transistor used in CE

configuration are hie = 1000Ω; hfe = 150; hre = 1.2 X 10-4; hoe =

25 X 10-6 ohms. The transistor has a load resistance of 10 KΩ in

the collector and is supplied from a signal source of resistance 5

KΩ. Compute the value of input impedance, output impedance,

current gain and voltage gain.

Or

(b) (i) From the CE configuration output characteristics, explain

the three region of operation of a tranistor. (10)

(ii) How could a transistor act as a switch (6)

12. (a) Explain CB Transistor configuration with input and output

characteristics.

Or

(b) Explain in detail about power transistors and its characteristics.


13. (a) (i) Discuss the behavior of PN Junction under forward and

reverse bias condition. (10)

(ii) Describe the effect of temperature on PN Junction diode

characteristics. (6)

Or

(b) (i) Explain how a PN Junction possesses various capacitances

and also discuss the effect of these capacitances. (10)

(ii) Explain the following

(1) Storate time

(2) Transistion time

(3) Reverse recovery time. (6)

14. (a) Explain the input and output characteristics of a common

base BJT configuration. Also draw the characteristics curves.

Or

(b) Using the hybrid equivalent model, analyse and deduce the

expression for the parameters using the circuit sketch. What is the

significance of this approach?

15. (a) For common emitter-bipolar junction transistor

configuration, analyze the input and output characteristics. Also,

give the inferences and analytical expressions for the same. (16)

Or


(b) Write a note on

(i) Transistor construction (4)

(ii) Voltage gain and current gain expressions for CB Configuration

using transistor hybrid model. (Figures are necessary) (12)

UNIT 3

PART A 1. Differentiate FET and BJT (any two). 2. List the JFET parameters. 3. Why do you call FET as field effect transistor? 4. Define Pinch off voltage. 5. Distinguish between BJET and FET. 6. What is called intrinsic standoff ratio in UJT? 7. Differentiate between BJT and JFET’s. 8. Give any two application of UJT. 9. Define pinch off voltage. 10. Give the drain current equation of JFET.

PART – B

11. (a) (i) Compare JFET and MOSFET. (any five) (5)

(ii) Give a detailed description of construction and operation of JFET (11)

Or

(b) (i) Explain the operation of UJT hence draw its VI characteristics

(10)


(ii) Draw the equivalent circuit of UJT and define the intrinsic stand off

ration.

12. (a) Explain the operation of enhancement mode MOSFET with neat

diagram and compare it with JFET.

Or

(b) (i) Describe the working principle of UJT. (12)

(ii) What are unipolar and bipolar devices? Give examples. (4)

13. (a) (i) Describe the input, output characteristics of a transistor in CB

configuration. (10)

(ii) Compare CE, CB and CC configurations with respect to impedances and

gain. (6)

Or

(b) (i) Derive the expressions of input impedance, output impedance,

voltage and current gain in CE configuration using hybrid model. (12)

(ii) If the base current of a transistor is 20μA and collector current is 6.38mA

, calculate α and β of a transistor. (4)

14. (a) Explain the construction, working and operating characteristics of N-

Channel JFET’s with relevant diagrams. Give the application of JFET’s.

Or

(b) Explain the construction and working of the unijunction transistor. What

is the significance of the operating VI characteristics of UJT. Draw the

relevant diagrams.


15. (a) With neat diagram explain the construction, working characteristics

of Unijunction transistor. Give its equivalent circuit. (16)

Or

(b) Write the construction, operation and characteristics behavior of JFET

under various biasing conditions. Give necessary figures. (16)

UNIT 4

PART A

1. Define fill factor.

2. Distinguish between photo diode and LED.

3. What is the principle behind solar cell?

4. Name any four Optoelectronic Devices.

5. What is a LED? Mention the elements used for making LEDs.

6. What is known as dark current and dark resistance of

photodiodes?

7. Give any two applications of liquid crystal cells.

8. What is the difference between LED’s and Photo diodes?

9. Differentiate a PN junction diode and LASER diode.

10. List the applications of optoelectronic devices.

PART – B

11. (a) (i) Describe the operation of a photo transistor. (6)

(ii) Discuss the two methods and the two modes of LCD that are used to control properties of light (10)

Or

(b) Brief the following


(i) Opto Couplers (8)

(ii) Solar Cell (8)

12. (a) Explain the construction and characteristics of LED.

Or

(b) Explain the function of Phototransistor and state its applications.

13. (a) (i) Explain the construction and characteristics of a photo diode. Mention the applications of Photodiodes. (10)

(ii) Discuss the behavior of a phototransistor. (6)

Or

(b) (i) What is a photo conductive cell? Briefly give its construction and characteristics. (8)

(ii) What is an opto coupler? Explain its working principle. (8)

14. (a) Write a detailed note on :

(i) LED’s (8)

(ii) Phototransistor. (8)

Or

(b) Explain the construction, working and VI characteristics of a Phototransistor. Bring out the difference between phototransistor and photodiodes.


15. (a) What is the physics of photo emissivity. Explain in detail, the construction and working of any one optoelectronic device which uses this principle. (16)

Or

(b) Give a detailed account on:

(i) Opto couplers and their applications (8)

(ii) Photo transistors and diodes (8)

UNIT 5

PART A

1. Realize a SCR using two transistors.

2. Draw the equivalent circuit of a varactor diode.

3. Draw the symbol of tunnel diode and state its applications/

4. What is Zener Breakdown?

5. Illustrate the concept of Piezo electric effect.

6. Discuss the principle of operation of varactor diode

7. Why are zener diodes employed as voltage regulations?

8. What is the significance of a varactor diode?

9. Draw the transistor equivalent circuit of SCR.

10. What is LDR?


PART – B

11. (a) (i) Give an account for charge coupled devices (6)

(ii) Narrate the operation of zener diode and define Zener

breakdown. Draw its VI characteristics. (10)

Or

(b) (i) Differentiate SCR and TRAIC. (6)

(ii) With the energe band diagram explain the VI characteristics of

Tunnel diode. (10)

12. (a) Explain the operations of SCR in detail and compare it with

TRIAC.

Or

(b) Explain the function of varactor diode and state the

applications.

13. (a) (i) Explain the characteristics of Zener diode as a regulator.

(6)

(ii) Discuss in detail the behavior of tunnel diode and its

applications. (10)

Or

(b) (i) Distinguish between SCR and TRIAC. (6)


(ii) Describe the characteristics of

(1) Thermistors

(2) LDR. (10)

14. (a) Give the theory of construction, working and VI

characteristics of SCR. List out the applications of it.

Or

(b) Discuss about the construction, working and operating

characteristics of a tunnel diodes. What is the salient feature of

this diode?

15. (a) (i) Define tunneling phenomenon. Explain how tunnel

diode operates under different operating conditions. In what way

it is different from the conventional diodes? Give the necessary

energy level diagrams. (12)

(ii) Give the characteristics features of devices belonging to the

thyristor family. (4)

Or

(b) (i) Zener diode can be used as a voltage regulator-Justify it. (8)

(ii) Write a note on PUT. (8)

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