Analog Electronics 2 - May 2013

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 Design two stage cascaded amplifier to meet the following specifications:
A_v ≥ 600, Ri ≥ 1MΩ, S_ico ≤ 10, f_L = 20Hz, Vo = 3V.
What would be the voltage gain for designing the circuit if both bypass capacitors are removed? To design, use suitable transistor from data sheet.(20 marks) 2 (a) Design a class B push-pull amplifier with appropriate biasing to minimize cross over distortion and using transformer coupling ratio for 8W of power. Use 12V DC supply. Assume R_L = 5Ω. For designing circuit find efficiency at full load. (15 marks) 2 (b) A BJJ has gm = 38m℧, rb^'e = 5.9 kΩ, h_ie = 6kΩ, rbb' = 100Ω, Cb'c = 12 pF, cb'e = 63 pf and h_fe = 224 and 1 KHz. Calculate α and β cut-off frequencies and f_T.(5 marks) 3 (a) Explain Millers theorem.(5 marks) 3 (b) For a cascaded amplifier, show that the overall lower 3db freq F_LT and higher 3dB frequency F_H with n stages. Where
and (10 marks) 3 (c) Determine the maximum safe power dissipation in a transistor if the rated power is 25W, maximum junction temperature T_jmax = 125^?C. The transistor is mounted on a heat sink with ?_cs = 1^?C/W and ?_sa = 5^?C/W. (5 marks) 4 (a) From the circuit determine value of resistors R_e and R₁, such that the operating point I_cq = 10V and V_ceq = 10V.
Given value of R₂ = 10K, β =100 and V_BE = 0.7V
(10 marks) 4 (b) Draw the circuit of Darlington configuration and obtain expression for current gain and input resistance. Also explain the principle of Bootstrapping with the help of appropriate diagram.(10 marks) 5 (a) From the given circuit, V_BE = 0.6, β_ac = β_dc = 100

find (1)Q point (2)Ad (3)Ac (4)CMRR (8 marks) 5 (b) Derive the expression for R_if and R<subof< sub=""> using equivalent circuit for -
(i) Voltage series negative feedback.
(ii) Current shunt negative feedback.</subof<></span>(12 marks) 6 (a) Explain Barkhausen's criteria. Also derive the expression for frequency of oscillation of Wein Bridge Oscillator.(10 marks) 6 (b)(i) Write short note on: Colpitt's Oscillator.(5 marks) 6 (b)(ii) Write short note on: Clapp Oscillator.(5 marks) 7(a) For the above circuit, compute voltage levels ad sketch the waveform of voltages at B₁, C₂ and B₂, C₂ for permanent state and quasi stable state.

Use silicon transistors with r_bb = 100Ω and h_FE = 30(10 marks) 7(b) Explain the various negative feedback topologies.(10 marks)