Electronics and Communication Technology (January – 2014) [IDOL - Revised Course | Question Paper]

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B.Sc.IT: Semester – I

[Electronics and Communication Technology]

Question Paper (January – 2014) [Revised Course]

Time: 3 Hours
Total Marks: 100

N.B.:    (1) All Questions from 1 to 7 are Compulsory.
             (2) Figure To right indicate the marks.

Q.1 Attempt The Following Question: (10 Marks)
(A) Explain the formation of P-Type Semiconductor with necessary diagram.
(B) Draw a neat labeled block diagram of an oscillator.
(C) Explain working of transistor as a switch.
(D) Define AM and draw the waveform.
(E) State the Sampling Theorem and explain it.

Q.2 (A) Attempt Any Two From The Following: (10 Marks)
(i) Explain the working of P-N Junction diode with necessary diagrams.
(ii) With the help of circuit diagram explain the working of half wave rectifier with necessary wave-forms.
(iii) Explain the output characteristics of N-P-N transistor in CE configuration.

Q.2 (B) Attempt Any One From The Following: (5 Marks)
(i) The turns ratio of a transformer uses in a bridge rectifier is 100:1. The primary is connected to a 230 VRMS mains supply. Assuming diode voltage drop to be 0.5 V, find the dc voltage across the load resistance & the PIV of each diode. Also find the load current if a load resistance of 100 Ω is used.
(ii) When the emitter current of a transistor is changed by 1.1 mA its collector current changes by 0.97 mA. Calculate its common base current gain(β)  and common emitter current gain(α).

Q.3 (A) Attempt Any Two From The Following: (10 Marks)
(i) Explain the working of single stage CE Amplifier. Also discuss its frequency response curve.
(ii) With the help of circuit diagram explain the working of multistage amplifier. Derive an expression for its gain decibel.
(iii) Explain working of RC coupled amplifier with circuit diagram discuss its frequency response curve.

Q.3 (B)  Attempt Any One From The Following: (5 Marks)
(i) Explain the need of biasing a transistor. Explain the fixed biased method of biasing.
(ii) Explain how to plot the load line of CE Amplifier. What is Q-Point.

Q.4 (A) Attempt Any Two From The Following: (10 Marks)
(i) Explain the need of tank circuit in an oscillator. Explain the RC tank circuit.
(ii) Explain the working of RC phase shift oscillator with its circuit diagram.
(iii) Explain the block diagram of IC555.

Q.4 (B)  Attempt Any One From The Following: (5 Marks)
(i) An astable multivibrator using IC555 has R_A=470 Ω,R_B=2kΩ and C=0.0076μF. Calculate charging and discharging time constant duty cycle and output frequency.
(ii) A Colpitt’s Oscillator uses following components in its tuned C_1=1500pF,C_2=800pF,L=200μH. Calculate the frequency of the oscillator.

Q.5 (A) Attempt Any Two From The Following: (10 Marks)
(i) With the help of circuit diagram explain the working of Balanced Modulator.
(ii) Explain the block diagram of the basic communication system.
(iii) Explain filter method for side band suppression with block diagram.

Q.5 (B) Attempt Any One From The Following: (5 Marks)
(i) An audio signal is given by E_m=100 sin⁡(3140)t. It amplitude modulates a carrier given by E_c=125 sin⁡〖4×〖10〗^6 t〗. Find modulation index, percentage modulation, frequency of carrier, frequency of modulating signal, amplitude of side band components & their frequency.
(ii) Explain the low level modulator.

Q.6 (A) Attempt Any Two From The Following: (10 Marks)
(i) With help of block diagram explain the Television Transmitter.
(ii) Explain TRF receiver with the block diagram.
(iii) Compare FM and AM Systems.

Q.6 (B) Attempt Any One From The Following: (5 Marks)
(i) Explain typical Pre-Emphasis & De-Emphasis circuit with their characteristics.
(ii) Explain PPM generator with waveform.

Q.7 (A) Attempt Any Two From The Following: (10 Marks)
(i) Explain Amplitude Shift Keying.
(ii) Explain types of Optical Fiber.
(iii) Explain the Optical Links in detail.

Q.7 (B) Attempt Any One From The Following: (5 Marks)
(i) Explain the construction and working of LED.
(ii) Write a note on Ray Model.

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