**B.E./B.Tech. DEGREE EXAMINATION, JUNE 2010**

Second Semester

Computer Science and Engineering

EC2151- ELECTRIC CIRCUITS AND ELECTRON DEVICES

(Regulation 2008)

(Common to Biomedical Engineering, Electronics and Communication Engineering and Information Technology)

Second Semester

Computer Science and Engineering

EC2151- ELECTRIC CIRCUITS AND ELECTRON DEVICES

(Regulation 2008)

(Common to Biomedical Engineering, Electronics and Communication Engineering and Information Technology)

**Time: Three hours Maximum: 100 Marks**

**Answer ALL Questions**

PART A- (10 X 2 = 20 Marks)

PART A- (10 X 2 = 20 Marks)

1. State Kirchoff's current law and voltage law.

2. State Superposition theorem.

3. What is quality factor?

4. Find the resonant frequency in the ideal parallel LC circuit shown in figure.

5. Give the expression for transition capacitance and diffusion capacitance of a PN diode.

6. Define avalanche breakdown.

7. What is "Early effect" in CB configuration and give its consequences?

8. Distinguish clearly the difference between N with P channel FETs.

9. Give some applications of tunnel diode.

10. What is meant by photovoltaic cell?

1. State Kirchoff's current law and voltage law.

2. State Superposition theorem.

3. What is quality factor?

4. Find the resonant frequency in the ideal parallel LC circuit shown in figure.

5. Give the expression for transition capacitance and diffusion capacitance of a PN diode.

6. Define avalanche breakdown.

7. What is "Early effect" in CB configuration and give its consequences?

8. Distinguish clearly the difference between N with P channel FETs.

9. Give some applications of tunnel diode.

10. What is meant by photovoltaic cell?

**PART B- (5 X16 = 80 Marks)**

11. (a) (i) State Thevenin's and superposition theorems, mention one application. (8 Marks)

(ii) Find the Thevenin's equivalent of the circuit shown in figure. (8 Marks)

11. (a) (i) State Thevenin's and superposition theorems, mention one application. (8 Marks)

(ii) Find the Thevenin's equivalent of the circuit shown in figure. (8 Marks)

**(b) (i) Consider the circuit in figure. (12 Marks)**

(1) If Rout = 3Kohm, find the power delivered to it.

(2) What is the maximum power that can be delivered to any Rout?

(3) What two different values of Rout will have exactly 20mw delivered to them?

(ii) State maximum power transfer theorem. (4 Marks)

12. (a) In the circuit shown in figure, determine the complete solution for the current when the switch is closed at t =0. Applied voltage is v(t) = 400cos(500t + ^/4), resistance R = 15ohm, inductance L = 0.2H and capacitance C = 3 Uf. (16 Marks)

(b) (i) Explain (using the relevant circuit) the double tuned circuit and derive the expression for A and Mc. (10 Marks)

(ii) The tuned frequency of a double tuned circuit shown in fig. is 10^4 rad/sec. If the source voltage is 2v and has a resistance of 0.1 ohm, calculate the maximum output voltage at resonance if R1= 0.01 ohm, L1= 2UH, R2 = 0.1 ohm and L2 = 25UH. (6 Marks)

13. (a) (i) Derive the PN diode current equation. (8 Marks)

(ii) Explain how the depletion region at a p-n junction is formed and explain with relevant sketches for charge density, electric field intensity and potential energy barriers at the junction. (8 Marks)

(ii) Draw the Zener regulation circuit and explain its function for input and output regulation. (8 Marks)

14. (a) Explain the input and output characteristics of a common emitter configuration with a neat sketch. (16 Marks)

(b) What is MOSFET? Explain the construction and working principle of enhancement mode and depletion mode MOSFET with a neat diagram. (16 Marks)

15. (a) What is tunneling phenomenon? Describe the V-I characteristics and concepts of tunnel diode with application. (16 Marks)

(b) Explain the negative resistance characteristics of Unijunction Transistor with neat sketch. (16 Marks)

(1) If Rout = 3Kohm, find the power delivered to it.

(2) What is the maximum power that can be delivered to any Rout?

(3) What two different values of Rout will have exactly 20mw delivered to them?

(ii) State maximum power transfer theorem. (4 Marks)

12. (a) In the circuit shown in figure, determine the complete solution for the current when the switch is closed at t =0. Applied voltage is v(t) = 400cos(500t + ^/4), resistance R = 15ohm, inductance L = 0.2H and capacitance C = 3 Uf. (16 Marks)

**(Or)**

(ii) The tuned frequency of a double tuned circuit shown in fig. is 10^4 rad/sec. If the source voltage is 2v and has a resistance of 0.1 ohm, calculate the maximum output voltage at resonance if R1= 0.01 ohm, L1= 2UH, R2 = 0.1 ohm and L2 = 25UH. (6 Marks)

13. (a) (i) Derive the PN diode current equation. (8 Marks)

(ii) Explain how the depletion region at a p-n junction is formed and explain with relevant sketches for charge density, electric field intensity and potential energy barriers at the junction. (8 Marks)

**(Or)**

**(b) (i) Draw the Zener diode characteristics and explain the working o Zener diode. (8 Marks)**

14. (a) Explain the input and output characteristics of a common emitter configuration with a neat sketch. (16 Marks)

**(Or)**

15. (a) What is tunneling phenomenon? Describe the V-I characteristics and concepts of tunnel diode with application. (16 Marks)

**(Or)**

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