Analog Electronics 2 - Dec 2012
Electronics & Telecomm. (Semester 4)
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) Design two stage RC coupled CE amplifier for the following specifications:
Av ≥ 1600, Vo = 3.2V. Use BC 147A transistor from data sheet. (Assume for BJT hre = hoe =0)(15 marks) 1 (b) For the above designed amplifier find voltage gain, input impedance, o/p impedance and total current by Vcc. (5 marks) 2 (a) Design class A transformer coupled power amplifier with the following specifications:
Peak O/p Voltage = 6V, Load Resistance RL = 6Ω and VCC = 20V. (10 marks) 2 (b) For dual i/p balanced o/p differential amplifier analyze and derive the expression for
(i) differential mode gain
(ii) common mode gain
(iii) CMRR.(10 marks) 3 (a) A three stage RC coupled amplifier uses FET with the following parameters:
gm = 2.6 mA/V; rd = 7.7 kΩ, RD = 12kΩ and RG = 1MΩ, Coupling Capacitor is Cc = 0.005 μF and Cs = ∞. Evaluate -
(i) The overall mid-band voltage gain in dB.
(ii) Lower 3dB frequency of individual stages.
(iii) Overall lower 3dB frequency of amplifier.(10 marks) 3 (b) Discuss Darlington pair. What are its primary features? Obtain expression for Av, Ai, Ri. (10 marks) 4 (a) For the amplifier shown in figure, derive the expression Avf, Aif, Rif and Rof using negative feedbak approach.
(12 marks) 4 (b) Explain the principle of working of Wein bridge oscillator circuit. Explain why negative feedback in addition to the usual positive feedback is employed in Wein bridge oscillator.(8 marks) 5 (a) An amplifier with negative feedback has an overall gain of 100. Variation of this gain of only (+-)1 percent can be tolerated for some specific use. If the open loop gain variations of +10% are expected owin to production spreads in device charactersitics, determie the minimum value of the feedback fraction B and also open loop gain to satisfy the above condition.(10 marks) 5 (b) Explain the practical cascade amplifier and derive the expression for Av, Ri, Ro. List application of cascade amplifier. (10 marks) 6 (a) Explain why a voltage amplifier cannot be used as a good power amplifier.(8 marks) 6 (b) With neat sketch, explain the working of an astable multivibrator. On what factors does the frequency of the output waves depend?(12 marks)
Write short notes on (any two):
7 (a) Crystal osciallator and its application.(10 marks) 7 (b) Explain low frequency response of RE coupled CE amplifier.(10 marks) 7 (c) Harmonic distortions in a power amplifier and prove that P = (1+D2)P1.(10 marks)