Elec Circuits & Comm. Fundamentals - May 2014

Computer Engineering (Semester 3)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1 (a) Explain input offset voltage, CMRR and SVRR for operational amplifier.(5 marks) 1 (b) Explain Barkhausen's criteria for principle of oscillation.(5 marks) 1 (c) Explain principle of FDM.(5 marks) 1 (d) Compare FM and AM.(5 marks) 2 (a) Sketch a typical drain characteristics for V_GS=0 for an n-channel JEFET. Explain the shape of the characteristics, identify regions and indicate the important current and voltage levels.(10 marks) 2 (b) Explain class C BJT power amplifier in detail. Compare it with class A BJT power amplifier.(10 marks) 3 (a) Explain amplitude modulation for more than one modulating signal in following cases.
(i) Mathematical equation
(ii) AM waveform
(iii) Am amplitude and power spectrum
(iv) Modulation coefficient
(v) Transmission power
(10 marks) 3 (b) Explain with block diagram AM superheterodyne receiver.(10 marks) 4 (a) Explain ideal as well as practical differentiator wing operational amplifier in detail.(10 marks) 4 (b) The antenna current of an AM broadcast transmitter, modulated to a depth of 40% by an audio sine wave is 11 A. It increases to 12 A as result of simultaneous modulation by another audio sine wave. What is the modulation index due to this second wave ?(10 marks) 5 (a) State sampling theorem. What happens if the sampling is done at less than 2f_max'.(10 marks) 5 (b) What is multiplexing in communication system? Draw block diagram of TDM-PCM system and explain?(10 marks) 6 (a) Explain PLL as a frequency synthesizer.(5 marks) 6 (b) Explain operating principle of PLL.(5 marks) 6 (c) List different types of ADC's and explain binary weighted ADC in detail.(10 marks)