JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year BASIC ELECTRONICS Previous Question Paper (May/June - 2019 - 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 and may have a, b, c as sub questions.
PART - A
Define reverse saturation current and knee voltage of a diode.
Answer
Reverse saturation current (I₀) is the small, constant current that flows through a diode when it is reverse-biased, caused by the drift of minority charge carriers. The knee voltage (or cut-in voltage) is the forward bias voltage at which the diode begins to conduct current significantly and the forward current increases rapidly.
In a filtered bridge rectifier, the power supply transformer has a turns ratio of 10:1 and the primary is connected to 115 V rms, 60 Hz supply. The filter consists of C=50µF and RL= 2.2 KΩ. Determine ripple factor.
Answer
Given: Turns ratio = 10:1, V_p = 115 V, C = 50 µF, R_L = 2.2 kΩ, f = 60 Hz. The secondary voltage V_s = 115 / 10 = 11.5 V rms. The peak voltage V_m = 11.5 × √2 = 16.26 V. The ripple factor for a capacitor filter is given by:
Substituting the values: r = 1 / (4 × 1.732 × 60 × 50 × 10^-6 × 2200) = 1 / (4.56) ≈ 0.219 or 21.9%.
Obtain the relation between IB, IE and Ic in a transistor.
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What are small signal amplifiers? How are they different from large signal amplifiers?
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List the applications of SCR.
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Bring out three differences between Diac and Triac.
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An amplifier has a gain of 60 and distortion 10 % without feedback. Determine gain and distortion with negative feedback if feedback factor being 6.
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In a phase shift oscillator, the three RC sections have same resistor and capacitor values, R= 400 KΩ and C= 50pF. Determine the frequency of oscillation.
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List the electronic welding controls used in resistance welding.
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Classify the timers according to the function and the technique used to achieve the industrial timing.
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PART - B
Explain the working of a diode as a switch.
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Explain the working of a full wave bridge rectifier with neat input and output waveforms.
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Draw the typical forward and reverse characteristics for a diode and explain.
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A center tapped transformer has a 220 V primary winding and a secondary winding rated at 12-0-12 V and is used in full wave rectifier with a load of 1000 Ω. What is DC output voltage, DC output current and PIV rating required for diodes?
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Compare three configurations of a bipolar transistor CB, CC and CE.
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Explain the working of a PNP transistor with the help of neat diagrams.
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What are the main purposes for which a common collector amplifier is used?
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With the help of neat diagrams explain the construction and working of an SCR.
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Why does an SCR not turn on in reverse biased condition?
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Explain the working of semi controlled 1- rectifier.
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Explain the working of Hartley oscillator with neat circuit diagram.
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Explain the effect of negative feedback on the bandwidth of an amplifier.
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Classify the negative feedback amplifier circuits and their effects on voltage gain, input resistance and output resistance.
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Explain the following type of Timers (i) Electro-mechanical Timers (ii)Electronic Timers.
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List different applications of Ultrasonic Waves and explain the principle and working of Pulsed-echo Ultrasonic Flow Detector.
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Explain the principle of working of any one type of Thermal Timers.
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Draw and explain piezo electric generator circuit using Hartley oscillator for generation of Ultrasonic waves.
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