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:
Av ≥ 600, Ri ≥ 1MΩ, Sico ≤ 10, fL = 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 RL = 5Ω. For designing circuit find efficiency at full load. (15 marks) 2 (b) A BJJ has gm = 38m℧, rb'e = 5.9 kΩ, hie = 6kΩ, rbb' = 100Ω, Cb'c = 12 pF, cb'e = 63 pf and hfe = 224 and 1 KHz. Calculate α and β cut-off frequencies and fT.(5 marks) 3 (a) Explain Millers theorem.(5 marks) 3 (b) For a cascaded amplifier, show that the overall lower 3db freq FLT and higher 3dB frequency FH 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 Tjmax = 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 Re and R1, such that the operating point Icq = 10V and Vceq = 10V.
Given value of R2 = 10K, β =100 and VBE = 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, VBE = 0.6, βac = βdc = 100
find (1)Q point (2)Ad (3)Ac (4)CMRR (8 marks) 5 (b) Derive the expression for Rif and R<subof< sub=""> using equivalent circuit for -
(i) Voltage series negative feedback.
(ii) Current shunt negative feedback.</subof<><>(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 rbb = 100Ω and hFE = 30(10 marks) 7(b) Explain the various negative feedback topologies.(10 marks)