Download VTU BE 2020 Jan Question Paper 18 Scheme 18ELIN1424 Basic Electronics First And Second Semester

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BCS SCHEME

18ELN14/24

First/Second Semester B.E. Degree Examination, Dec.2019/Jan.2020

Basic Electronics

Time: 3 hrs.

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Max. Marks: 100

Note: Answer any FIVE full questions, choosing ONE full question from each module.

Module-1

1. a. Explain the working of PN junction diode under forward and reverse biased conditions. (06 Marks)
2. b. Explain the working of Photodiode. (05 Marks)

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3. c. Explain with neat circuit diagram and waveforms, the working of full wave bridge rectifier. Show that the efficiency of full wave bridge rectifier is 81%. (09 Marks)

OR

1. a. Explain the operation of Half wave rectifier with capacitor filter with neat circuit diagram and waveforms. (06 Marks)
2. b. A full wave rectifier uses 2 diodes having internal resistance of 10 O each. The transformer RMS secondary voltage from center to each end is 200V. Find I_m and V_dc if the load is 800 O. (06 Marks)
3. c. Explain how zener diode helps in voltage regulation with neat circuit diagram. Give detail mathematical analysis. (08 Marks)

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Module-2

1. a. Explain the construction, working and characteristics of n-channel JFET. (09 Marks)
2. b. With a neat circuit diagram, explain the working of CMOS Inverter. (06 Marks)
3. c. For a n-channel JFET if I_DSS = 9 mA and V_p = -6V. Calculate I_D at V_GS = -4V and V_GS at I_D = 3 mA. (05 Marks)

OR

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1. a. Explain the construction, working and characteristics of enhancement type MOSFET. (09 Marks)
2. b. Explain the working of Silicon Controlled Rectifier [SCR] using two transistor model. (06 Marks)
3. c. For an EMOSFET, determine the value of I_D if I_D(on) = 4 mA, V_GS(on) = 6V, V_T = 4V and V_GS = 8V. (05 Marks)

Module-3

1. a. What is an OP-AMP? List the characteristics of an ideal OP-AMP. (06 Marks)

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2. b. Explain the operation of an OP-AMP as inverting amplifier with neat diagram and waveforms. (06 Marks)
3. c. Explain how OP-AMP can be used as (i) Integrator (ii) Voltage follower. (08 Marks)

OR

1. a. Explain the different input modes of an OP-AMP. (06 Marks)
2. b. Design an adder circuit using OP-AMP to obtain an output voltage, V_o = —[2V₁ + 3V₂+5V₃]. Assume R_f=10kO. (06 Marks)

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3. c. Explain the following terms with respect to OP-AMP: (i) CMRR (ii) Slew rate (iii) Input bias current (iv) Supply Voltage Rejection ratio. (08 Marks)

Module-4

1. a. With a neat circuit diagram, explain how transistor is used as an amplifier. Derive an equation for A_v. (08 Marks)
2. b. Explain RC phase shift oscillator with circuit diagram and necessary equations. (08 Marks)
3. c. Explain the voltage series feedback circuit and derive an equation for voltage gain, A_v, with feedback. (04 Marks)

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OR

1. a. With a neat circuit diagram, explain the working of Wein-bridge oscillator. (08 Marks)
2. b. Explain the operation of I.C555 as an Astable oscillator with neat circuit diagram and necessary equations. (08 Marks)
3. c. The Transistor in CE configuration is shown in Fig.Q8(c) with R_C = 1 kO and ß_DC = 125. Determine (i) V_CE at V_in = 0 V (ii) I_B(min) to saturate the collector current (iii) R_B(max) when V_in = 8 V. (V_CE(sat) can be neglected). (04 Marks)

Fig.Q8(c)

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Module-5

1. a. Design Full adder circuit and implement it using basic gates. (08 Marks)
2. b. Find (i) (1101 0111 0110 1010)₂ = ( ? )₁₀ (ii) (EB986)₁₆ = ( ? )₂ (iii) (925.75)₁₀ = ( ? )₈ (06 Marks)
3. c. Explain the basic elements of communication system with block diagram. (06 Marks)

OR

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1. a. State and prove De-Morgan's theorem. (06 Marks)
2. b. With a block diagram, explain the working of a 3-bit ripple counter. (06 Marks)
3. c. What is a Flip-flop? Explain the operation of master-slave JK flip-flop. (08 Marks)

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