VTU Question Papers Basic Electronics First Second Semester B E Degree Examination June July 08

VTU  Question Papers Basic Electronics

First / Second Semester B.E. Degree Examination June / July 08

; i a. With the help of an energy band diagram, explain an insulator, semiconductor and a conductor.                    (06 Marks)

  1. Distinguish between ‘drift current’ and ‘diffusion current’ in a PN device.                                                 (06 Marks)
  2. Show that a diode is capable of rectification. Draw the circuit of bridge rectifier. Explain its working. (08 Marks)

2            a. Explain the working of a Zener Regulator.                                                                                                            (06 Marks)

  1. Explain the terms load regulation and line regulation.                                                                                     (06 Marks)
  2. Design a Zener Regulator for the following specification:

Output voltage = 5 V, Load current =10 mA, Zener Wattage = 400 mW, Input voltage = I0V±2V.    (08 Marks)

3            a. Draw and explain the characteristics of a transistor in CE-configuration. Show the different

regions of operation.                                                                                                                                               (05 Marks)

  1. Explain the biasing requirements for transistor to operate in different regions. (05 Marks)
  2. Explain the working of a two-stage RC-coupled amplifier with the help of a neat diagram and sketch the frequency response showing different regions and bandwidth. (10 Marks)

4            a. With the help of a circuit diagram, briefly explain the working of Hartley Oscillator. State

the conditions for oscillation.                                                                                                                                (10 Marks)

  1. Explain why coupling in amplifier is necessary. Mention the four basic methods of coupling.               (06 Marks)
  2. In a Colpitts oscillator Ci = C2 = C and L = 100 fill, frequency of oscillation = 500 kHz. Determine C.       (04 Marks)

5            a. List the characteristics of an ideal op-amp.                                                                                                           (06 Marks)

  1. Define the following terms with rcspect to op-amp:

i) CMRR ii) Slew rate iii) Virtual ground.                                                                                                             (06 Marks)

  1. Explain the need for modulation and list different types of modulation schemes. (08 Marks)

6            a. With a neat diagram, and relevant waveforms explain the working of a super heterodyne

receiver.                                                                                                                          (10 Marks)

  1. A carrier of 1 MHz with 400 W of power is amplitude – modulated with a sinusoidal signal of 2500 Hz. The depth of modulation is 75%. Calculate the sideband frequencies, bandwidth and power in sidebands and total power in modulated wave.                                                                                                                                                                         (06 Marks)
  2. Distinguish between AM and FM.                                                                                                                        (04 Marks)

7            a. Simply the following Boolean expressions and realize them using NAND gates:

i)          y=ABC+ABC+AB+AC

ii)               y = (a + Bc)(a + B + c|A + b)                                                                                                                   (10 Marks) b. Explain with a neat block diagram and necessary diagrams the measurement of amplitude

frequency and phase of a given signal using CRO.                                                                                          (10 Marks)

8            a. Perform the following:

i) 342.56to – (?>2 ii) (10 AB)i« = (?)io iii) (8000)10 – (?)i6                                                               iv) Subtract (1101)2 from

(1010)2 using 2’s complement.                                                                                          (10 Marks)

  1. State and prove De-Morgan’s theorem.                                                                                                                 (05 Marks)
  2. Compare the performance of different logic families.                                                                                        (05 Marks)

*****

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