Visvesvaraya Technological University (VTU) 2005 B.E Electrical and Electronics Engineering 3rd SEM / ELECTRONIC CIRCUITS - Question Paper
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USN Mill 1111 Third Semester B.E. Degree Examination, January/February 2005
Time: 3 hrs.] (Max.Marks : 100
Note: 1) Answer any FIVE full questions.
2) All questions carry equal marks.
3) Missing data, if any may suitably be assumed giving valid reasons.
1. (a) Explain the validity of the piecewise linear approximation of the diode model
(b) For the clipping circuit shown in the following figure, obtain its transfer characteristic. Assume ideal diode. The input varies linearly from 0 to 150 vlts(-7MarksJ
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(c) Design. a fuJl wave rectifier with a capacitor filter to meet the following specifications
DC output voltage = 15 volts, Load resistance = Ifcft RMS ripple voltage on capacitor = < 1% of DC O/p voltage.
Assume the AC supply voltage as 230 Volts 50 Hz. (B Marks)
2. (a) Distinguish clearly between bias compensation and bias stabilization. Explain
how compensation is provided for USE & ICO in transistor circuits, do Marks)
(b) Design a voltage divider bias circuit using a silicon transistor with Vcc = +18 V, Ic = 2.3mA, VQE = 8.2 volt, Rc = 3.3/sft, 0 = 100 &
3. (a) Derive expressions for AV, Aj, Rin & R{] of an emittar follower. (io Marks!
(10 Marks)
4. (a) Draw the hybrid tt model of a transistor and explain the significance of each component in tlie model. ' (6 Marks)
(b) What are the types of distorsion in amplifiers ? Explain. [7 Marks)
(c) With the usual notations, show that the low-3db frequency of an Rc coupled transistor amplifier is given by f r7- (7 Marks)
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5. (a) Derive an expression for die input resistance of
i) Current series feedback amplifier ii) Voltage shunt feedback amplifier (b) i) For the circuit shown, find the a.c. voltage as a function of (1D Macks
V3 and Vj. Assume that the inverting amplifier input resistance is infinite, that
A = Av = -1000; p = Rs = Rc = Rg = hie = lfcfi,
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hre = hoe 0 & hjre 100 | |
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(10 Marks)
(a) Derive an expression for the maximum conversion efficiency of a class B push pull amplifier. (10 Marks)
6.
(b) A power transistor operating as class A in the circuit shown below is required to deliver a maximum of 5 watts to a 4f) load. (R = 4H). The quiescent point is adjusted for symetrical clipping and the collector supply voltage is Vcc = 20volts. Assume ideal characteristics with Vmn=>0
No
What is the transformer turns ratio n =
i)
ii)
iii)
iv)
What is the peak collector current Im ?
What is-the quiescent operating point -Ig, Vq ? What is the.collector circuit.efficiehcy ?
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(10 Mar.i) |
7. (a) With the usual notations derive an expression for the voltage gain of a practical inverting op. amp. (7 Marks)
(b) Design a first order high pass filter (Butterworth type) to have a pass band gain of 4 and a cut off frequency of 2 kHz. Draw the circuit schematic of designed circuit. ' (6 Marks)
(c) Design an OP-amp schmitt trigger (inverting type) to next the following specification: UTP +2V, LTP = -AV. & Output voltage swings between 10 volts. If the input is V- = 5sinwt} plot the waveforms of the input and output. (7Marks)
(a) Explain the principle of operation of a ii - 2R ladder type D to A converter.
(b) Give tine circuit schematic of a 555 timer connected as an astable multivlUrafor? Describe its operation. Derive an expression for its period. (10 Marks)
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| Earning: Approval pending. |
