JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III BASIC ELECTRONICS Previous Question Paper (November/December - 2017 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
What is the effect of bias voltage on the depletion layer.
Answer
Forward bias reduces the depletion layer width by pushing majority carriers toward the junction, lowering the potential barrier. Reverse bias increases the depletion layer width by pulling majority carriers away from the junction, raising the potential barrier.
Explain the working of a half wave rectifier with capacitor filter.
Answer
A half-wave rectifier converts AC to pulsating DC. During the positive half-cycle, the diode conducts and charges the capacitor to the peak voltage. During the negative half-cycle, the diode is reverse-biased and the capacitor discharges through the load, maintaining a smoother output voltage compared to a rectifier without a filter.
Draw the circuit symbols of pnp and npn transistors and indicate the directions of currents.
Answer
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Draw the circuit of a common collector amplifier and explain its working.
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Draw the symbols of SCR, diac and triac.
Answer
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Explain the working of SCR as a half wave rectifier.
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Give the classification of oscillators.
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What are the advantages of negative feedback?
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What is a timer circuit?
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Give the principle of dielectric heating.
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Part B
Explain the working of a bridge rectifier with necessary circuit and waveforms.
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Explain the VI characteristics of a PN junction diode giving the diode current equation. What is reverse saturation current? How does it depend on temperature?
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Explain the input and output characteristics of a transistor in CE configuration.
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Analyze the CE amplifier using h-parameter equivalent circuit. Derive the expressions for (a) current gain, (b) input resistance, (c) output resistance, (d) voltage gain.
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Explain about phase controlled full wave rectification using relevant waveforms.
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Draw the structure of Triac. Draw the VI characteristics of triac and explain.
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Draw the circuit diagram of Colpitt’s oscillator and explain its working. What is its frequency of oscillation?
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Draw the voltage series feedback amplifier and derive the expression for its gain, input and output resistances. What is the effect of negative feedback on them?
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Give the principle of Induction heating.
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Explain the application of Induction heating for: i) Surface hardening of steel. ii) Annealing of brass and iron.
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Compare and contrast the following timers: a) Thermal Timers b) Electromechanical Timers c) Mechanical Timers d) Electrochemical Timers
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