 MORE IN Analog and Digital Electronics
VTU Computer Science (Semester 3)
Analog and Digital Electronics
December 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

1(a) Explain how transistor can be used as switch.
5 M
1(b) Determine the value of the resistors$R_{e}\ and\ R_{c}\ for \ the \ circuit\ show\ in\ Q1\ (b)\ given\ that\ R\ = \5k\Omega ,\ \beta = 200,V_{CEQ}=5\ V\ and\ I_{CEQ}\ =2\ mA\ for$the silicon made transistor. 8 M
1(c) Briefly discuss the working operation of silicon controlled rectifier.
7 M

2(a) Explain with neat sketches the operation and characteristics of N-channel DE-MOSFET>
8 M
2(b) Calculate the value of operating point for circuit shown in fig.Q2 (b) given that threshold voltage for the MOSFET IS 2v AND JD(ON)=6 mA for VGS(ON)=5 V 7 M
2(C) Write the advantages of MOSFET over JFET.
5 M

3(a) Briefly discuss with necessary diagrams the working operation, characteristic and parameters of light Emitting Diode.
10 M
3(b) A photo diode has a noise current of i fa responsivity figure of 0.5 A/W. Determine is Noise Equivalent Power (NEP) and Selectivity (D).
5 M
3(c) Briefly explain the working operation of opto-couplers.
5 M

4(a) Explain the effect of Bypass capacitors and coupling on the low frequency response of the transistor based amplifier.
6 M
4(b) Draw the hybrid equivalent circuit of transistor in all three configurations given that the hybrid parameters for the transistor are hie=1.5?,hie - 150,hie-1×10-4 and hoe=20 umhos.
10 M
4(c) What are the advantages of cascade amplifiers on overall frequency response of the amplifiers?
4 M

5(a) A power amplifier in class B operation provides a 20V peak output signal to 15Ω load the system operates on a power supply of 25 V. Determine the efficiency of the amplifier.
8 M
5(b) The total harmonic distortion of an amplifier reduces for 10% to 1% on introduction of 10% negative feedback.Determine the open loop and closed loop again values.
6 M
5(c) Explain the advantages of negative feedback in amplifiers.i
6 M

6(a) What are sinusoidal oscillators?Explain the Barkhausen criterion for sustained oscillations.
8 M
6(b) With a neat circuit diagram,explain the principal od operation of buffered RC phase shift oscillator.
5 M
6(C) Discuss briefly the working operation of Astable multivibrator using IC555 timer.
7 M

7(a) Explain with neat diagram and relevant waveforms,the principle of operation on inverting regulator.
8 M
7(b) The regulated power supply provides a ripple rejection of-80db.if the ripple voltage in the unregulated input 10 2V,calculate the output ripple.
6 M
7(c) Explain the important features and parameters of switched mode power supplies(SMPS)
6 M

8(a) What are active filters using op-amp? Explain first order low pass and high pass filters with again.
8 M
8(b) Explain with circuit the working operation of instrumentation amplifier.
7 M
8(c) Calculate the values ofR1,R2,C1,C2 and R3 if the filter had a cut off frequency fo 10 Khz. Q factor of 0.707 and input impedance not less than 10k ? for the fig.Q8 (c) shows a second order low pass filter built around a single operational amplifier. 5 M

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