LOYOLA – ICAM

COLLEGE OF ENGINEERING AND TECHNOLOGY (LICET)

Loyola College Campus, Nungambakkam , Chennai – 34

Branch: ECE Date: 28-04-2014

Semester: II Time: 8.00 - 11.00 a.m (3 Hrs)

MODEL EXAM

ELECTRONIC DEVICES (EC6201)

PART-A Answer all the Questions ( 6x2=12)

1. What is drift current? write the expression for drift current density.

2. The reverse saturation current of a silicon PN junction diode is 10µA.Calculate the

diode current for the forward-bias voltage of 0.6V at 25ºC.

3. What is cut-off and linear region in a transistor ?

4. A transistor has β=100. If the collector current is 40 mA, fin the value of emitter

current.

5. Compare BJT and JFET.

6. What is channel length modulation in MOSFET?

7. What is Dark current?

8. What is Peak Inverse Voltage (PIV).

9. What are the factors which determine the stability of a voltage regulator?

10. List out the types of GaAs Devices.

PART-B Answer all the Questions (5x16=80)

11. (i) Calculate the dynamic forward and reverse resistance of a PN junction diode when

the applied voltage is 0.25V at T=300K and I0=2µA. (6)

(ii) Derive an expression for the capacitance in a reverse biased PN-Junction. (10)

OR

12. With a neat sketch derive the PN diode current equation from the quantitative theory

of diode currents. (16)

13. Explain the operation of a transistor in CE configuration. Discuss the input and output

characteristics along with the required transistor parameters. (16)

OR

14. (i) Draw the h-parameter model of a CE transistor and discuss the parameters. (8)

(ii) Compare the typical characteristics of CE, CB and CC configuration. (8)

15. Explain the construction and operation of an N-Channel JFET with neat sketch. prove

that µ=rd x gm. (16)

OR

16. Discuss the small signal equivalent circuits of JFET and MOSFET. (16)

17. (i) Explain the working of the Zener diode as a voltage regulator. (10)

(ii) A 24V, 600mW Zener diode is used for providing a 24V stabilized supply to a

variable load. If the input voltage is 32V, calculate the value of series resistance

required and the diode current when the load is 1.2KΩ. (6)

OR

18. Explain the construction and operation of MESFET. Compare MOSFET and

MESFET. (16)

19. (i) With a neat sketch explain the operation of UJT. (10)

(ii) A full wave rectifier employs 2 SCRs and 2 diodes in bridge configuration to

rectify 230V, 50 Hz AC and give an output of 150V to a load of 10Ω. Find the

firing angle, the time during which the SCR remains OFF & the load current. (6)

OR

20. Discuss the construction and operation of DIAC and TRIAC. (16)