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SPPU Electronics and Telecom Engineering (Semester 3)
Electronic Devices & Circuits
May 2014
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

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Answer any one question from Q1 and Q2
1 (a) Explain what is meant by Thermal Runway in BJT circuits.
6 M
1 (b) The transistor in connected in CE amplifier with bypassed RE has R1=50 KΩ. R2=2 KΩ, RC=1 KΩ, RS=1 KΩ, RL=10 KΩ. Also h-parameters are hie = 1.1 KΩ, hfe=50, hoe=24 μ A/V, hre=2.5K× 10-4. Determine the value for Av, AI, Ri.
6 M

2 (a) Determine the operating point and draw DC and AC Load Line if VCC=12 V, R1=8 KΩ, R2=4 KΩ, RE=1KΩ, RC=1 KΩ, RL=1.5 KΩ. Assume VBE=0.7 V.
6 M
2 (b) Compare CE, CB and CC amplifier performance parameters.
6 M

Answer any one question from Q3 and Q4
3 (a) Draw hybrid -π CE Amplifier model at high frequency. Explain significance of each parameter.
6 M
3 (b) An amplifier has gain of 60 and distortion is 10 % without feedback. Determine: (i) Gain, (ii) Distortion, when negative feedback is applied. Assume feedback factor as 0.1
6 M

4 (a) Explain the effect of Emitter bypass capacitor on low frequency response of BJT amplifier.
6 M
4 (b) Explain RC Phase Shift Oscillator using BJT and determine the output frequency for R = 1 KΩ, C=0.01 μF.
6 M

Answer any one question from Q5 and Q6
5 (a) In a Class A amplifier VCE(max)=25 V, VCE(min)=5 V. Find the overall efficiency for: (i) series fed load, (ii) transformer load.
6 M
5 (b) With the help of neat circuit diagram, explain the operation of Class AB power amplifier. Explain the significance of Class AB.
7 M

6 (a) Draw and explain Transformer coupled Audio Power Amplifier. Derive the expression for its efficiency.
6 M
6 (b) A Class B push pull amplifier is supplied with VCC=50 V. The signal swings the collector voltage down to Vmin=10V. The total dissipation in both transistors is 40W. Find: i) Pin(dc), ii) Pα(x), iii) % η.
7 M

Answer any one question from Q7 and Q8
7 (a) Describe the internal capacitance and high frequency model of MOSFET.
6 M
7 (b) E-MOSFET biased in CS configuration has following parameters: R1=10MΩ, R2=6.8 MΩ, RD=2.2 K&OMega;, VDD=24 V, VT=3V, ID(ON)=5 mA, VGS(ON)=6 V. Determine the values for ID and VDS.
7 M

8 (a) Enlist biasing of EMOSFET in common source configuration and explain any one of them in detail.
6 M
8 (b) Explain various non-ideal current voltage characteristics of EMOSFET.
7 M


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