Pre University / PU Electronics Model Question Paper : Karnataka www.pue.kar.nic.in

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Document Described : Electronics Question Paper, Karnataka Question Paper

ELECTRONICS
Time : 3 Hours 15 Minutes ] [ Max. Marks : 90
Note : i) The question paper has four Parts A, B, C & D.
ii) Question No. 23 in Part C and Question No. 32 in Part D are
from practicals.
iii) Read the instructions given for each Part.

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PART – A :
Note : Answer all questions. 10 × 1 = 10
1. Which region of a transistor is moderately doped ?
2. Write one application of CC amplifier.
3. Define closed loop gain.
4. What is a comparator ?
5. What should be the minimum voltage gain of an amplifier in the case of Wien-bridge oscillator to produce sustained oscillation ?
6. Define signal to noise ratio.
9. What is an XNOR gate ?
10. Mention the basic function of transponder.

PART – B :
Note : Answer any ten questions. 10 × 2 = 20
11. Explain the need for biasing a transistor.
13. Draw the circuit diagram of opto-coupler.
14. The current gain of a transistor in CB mode is 0·995 and its base current
is 20 µA. Calculate its collector current.
15. Distinguish between negative feedback and positive feedback.
16. The output voltage of an amplifier reduces to 0·8 V when a negative feedback
of 2% is employed. If the net input voltage of the amplifier is 100 mV,
calculate gain of the amplifier without feedback.
17. Define slew rate of an operational amplifier. Write any two characteristics of an ideal op-amp.
19. Briefly explain how an ionosphere helps in transmitting radio signals over large distance.
20. Mention any four reasons for modulating a radio signal.
21. What is a weighted code ? Give an example.
22. What is Metropolitan Area Network ( MAN ) ? Write one advantage of voice mail.

PART – C :
I. Answer the following question : 1 × 4 = 4
II. Answer any five questions : 5 × 4 = 20
24. Explain, with a mathematical equation, as to how the operating point
is stabilized in potential divider bias. Why is it called universal bias ?
26. With a block diagram, derive an expression for the output impedance
of a voltage series feedback amplifier.
27. How is the oscillation initiated in an RC oscillator ? What are the
drawbacks of RC oscillator over LC oscillator ?
29. Derive an expression for the instanteneous voltage of an FM wave.

PART – D :
I. Answer the following question : 1 × 6 = 6
32. Describe an expreiment to realise NOT, OR, AND and XOR using
IC 7400 and to verify truth table. Draw the pin diagram of IC 7400.
OR
Draw the pin diagram of IC 741. Describe an experiment to study
op-amp as subtractor using dc source.

II. Answer any five questions : 5 × 6 = 30
33. a) With a circuit diagram, explain the working of direct coupled
amplifier. Show the frequency response. 4
b) In a cascaded amplifier voltage gains of first and third stages are
respectively 5 and 10. The overall gain is 400. Calculate voltage
gain of the second stage. 2

34. a) Derive the expressions for output resistance, input resistance ( looking at the source terminal ) and voltage gain of a single stage CE amplifier using re model. 4
b) The output resistance of a CE amplifier of voltage gain 200, is 2 kO. If the transistor is of silicon material, calculate its emitter current. 2
36. a) With a circuit diagram, explain the working of Colpitts oscillator.
Mention the expression for frequency of oscillation. 4
37. a) Draw the block diagram of SHDAM receiver and explain briefly
the function of each block. 4
b) In a SHDAM receiver, two signals of frequencies 600 kHz and 1450 kHz are received simultaneously. Calculate local oscillator and intermediate frequencies of the receiver. 2
38. Using Karnaugh map simplify the following expression: Y ( A, B, C, D ) = Sm ( 0, 1, 6, 7, 8, 9, 15 ) and the don’t care conditions d ( A, B, C, D ) = Sm ( 5, 14 ). Draw the NAND gate equivalent circuit to realise the simplified equation. 6
39. a) Draw the labelled block diagram of digital computer. Briefly explain the function of each block. 4
b) What is a half-adder ? Write the Boolean expression for the output of carry of the full adder. 2
40. a) Explain the concepts of frequency reuse and cell splitting in cellular systems. 4
b) What is interlaced scanning ? Write its main advantage over sequential scanning. 2

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