Tribhuvan University

Institute of Engineering

Examination Control Division

2070 Chaitra – Regular

Subject: Electronic Devices and Circuits (EX501)

Programme: BEL, BEX, BCT

Full Marks: 80

Pass Marks: 32

Figures in margin indicate Full Marks

(There may be minor errors while typing the questions. Please leave comment if any typos)

1. What is p-n junction diode? Explain the large signal models of p-n junction diode. [1+4]
2. Find the value of dynamic resistance if voltage in the diode is 650mv and Irs is 10pA = (10*10^-12A). Given n=2 and V1=25mV. 
3. Why common collector amplifier is also called emitter follower? Draw the common collector transistor amplifier circuit and find its input impedance, output impedance and voltage gain. 
4. Draw and describe the Ebears Moll model for BJT. 
5. Describe in brief the operation of BJT as a switch in cut off and saturation region. 
6. Describe the construction and working principle of EMOSFET with help of drain characteristics curve and mathematical expressions.
7. Find Id and Vds for the given circuit. The given data are: Vp = -4V and Idss = 10mA 
8. Derive an expression to obtain the transconductance of JFET. 
9. What is the maximum efficiency of class B amplifier? State the condition when it occurs. 
10. When are tuned amplifiers used? Draw class A tuned amplifier circuit and find its 3db bandwidth. [2+5]
11. Draw the circuit diagram of Complementary-Symmetry Class-AB amplifier. Using Darlington pair transistors. 
12. Write the applications of tuned LC oscillators. Draw the Colpitt’s oscillator circuit and derive the expression for frequency of oscillation. 
13. Draw AMV circuit using IC 555 or BJT. 
14. State Barkhausen Circuit for sin wave oscillator. 
15. Design a (10-25) V variable dc series voltage regulator using LM 317 IC. 
16. Draw the circuit of current limiting circuit in dc voltage regulator. 
17. Find voltage stability factor of series dc voltage regulator. 
We're always listening. 