PESIT BANGALORE SOUTH CAMPUS QUESTION BANK BASIC ELECTRONICS Sub Code: 17ELN15 / 17ELN25 IA Marks: 20 Hrs/ Week: 04 Exam Marks: 80 Total Hours: 50 Exam Hours: 03 Name of Faculty: Mr. Udoshi Basavaraj Module -1: Semiconductor Diodes and Applications THEORY QUESTIONS 1. Define the following 1.PN junction diode 2.Forward bias of diode 3.Reverse bias of diode 4.Cut in voltage 5.Forward voltage 6.Reverse saturation current 7.Forward resistance or static resistance 8.Dynamic resistance 9.Maximum forward current 10.DC Load line 11.Q point 12.Reverse recovery time 13.Rectifier 14.Voltage regulator 15.Rectification efficiency 16.Ripple factor 17.Peak inverse voltage 18.Regulation 19.Minimum zener reverse current 20. Maximum zener reverse current. 2. Explain the forward bias and reverse bias of single PN junction diode indicating barrier potential. 3. Explain the VI characteristics of silicon diode. 4. Explain the VI characteristics of germanium diode. 5. Construct a DC load line on forward characteristics of diode D, connected in series with load resistor R L across DC source. Find the coordinates of Q point and explain the need for DC load line analysis.
6. Explain the significance of reverse recovery time when a pulse is applied across diode. How reverse recovery time can be minimized? 7. Explain avalanche breakdown and zener breakdown. 8. With the help of block diagram explain different stages of power supply. 9. What is the need for rectifier? 10. What is the significance of transformer in power supply? 11. Explain the operation of half wave rectifier with relevant circuit diagram and waveforms. 12. What are the disadvantages of half wave rectifier? How it is overcome? 13. Explain the operation of cetertap full wave rectifier with relevant circuit diagram and waveforms. 14. What are the disadvantages of center tap full wave rectifier? How it can be overcome? 15. Explain the operation of full wave bridge rectifier with relevant circuit and waveform. 16. Explain the operation of half wave rectifier with C filter using relevant circuit diagram waveforms and formulas. 17. Explain the operation of center tap full wave rectifier with C filter using relevant circuit diagram waveforms and formulas. 18. Explain the operation of bridge wave rectifier with C filter using relevant circuit diagram waveforms and formulas. 19. Design voltage regulator using zener diode. DERIVATIONS 1. Derive an expression for average load current and load voltage of half wave rectifier 2. Derive an expression for average load current and load voltage of center tap full wave rectifier 3. Derive an expression for average load current and load voltage of bridge wave rectifier 4. Derive an expression for RMS load current and RMS load voltage of half wave rectifier 5. Derive an expression for RMS load current and RMS load voltage of center tap full wave rectifier 6. Derive an expression for RMS load current and RMS load voltage of bridge wave rectifier 7. Evaluate ripple factor of a half wave rectifier. 8. Evaluate ripple factor of a center tap full wave rectifier 9. Evaluate ripple factor of a bridge wave rectifier. 10. Prove that peak inverse voltage of half wave rectifier is peak input voltage. 11. Prove that peak inverse voltage of center tap full eave rectifier is twice the peak input voltage. 12. Prove that peak inverse voltage of bridge wave rectifier is peak input voltage. 13. Prove that efficiency η=40% for half wave rectifier. 14. Prove that efficiency η=80.2% for center tap wave rectifier. 15. Prove that efficiency η=80.2% for bridge wave rectifier PROBLEMS 1. A diode with its forward characteristics as shown below is connected in series with a resistance of 1kΩ and driven by dc voltage source. Dram DC load line and find co-ordinates of Q point. Draw DC load line and find coordinates of Q point.
2. Find the load resistance in the circuit shown using the diode forward characterstics provided 6mA 3. Find minimal fall time for voltage pulses applied to a diode with reverse recovery time of 4 ns. 4. Estimate the maximum reverse recovery time for a diode for an input pulse with 0.5μs fall time. 5. A FWR with capacitor is supplying resistive load of 1kΩ. If the filter capacitor is 500μF. Calculate ripple factor. 6. In a FWR, the input is 30-0-30 v transformer. The load and diode forward resistance are 100Ω and 10Ω respectively. Calculate average voltage, rectification efficiency and percentage regulation 7. A FWR with capacitor is supplying resistive load fo 400Ω in parallel with a capacitor 500μF. If the AC supply voltage is 230sin314t V. Calculate ripple factor and DC current.
8. Design a zener regulator with the fallowing specifications Unregulated dc input voltage Vi: 8-12 volts Load Current, I L =20mA Regulated dc output voltage Vo: 5 Volts Minimum Zener current Iz min: 5mA Maximum Zener current Iz max: 80 ma 9. Design a zener regulator with the fallowing specifications Unregulated dc input volyage Vi: 13-17 volts Load Current, I L =10 ma Dc output voltage Vo : 10 Volts Minimum Zener current Iz min: 5 ma Maximum power dissipation in zener, P zmax : 500mW 10. A diode with Vf=0.7v is connected as a half wave rectifier. The load resistance is 600Ω and the (rms) AC input is 24v. Determine the peak output voltage, the peak current and peak reverse voltage. 11. Design a zener regulator with the fallowing specifications Unregulated dc input volyage Vi: 10 volts ± 20% Load Current, I L =10mA Regulated dc output voltage Vo : 5 Volts Minimum Zener current Iz min: 5mA Maximum Zener current Iz max: 80 ma TRANSISTORS 1. Explain the word transistor. Clearly show the biasing arrangement of the PNP an NPN transistor for conduction. 2. Give the concept of DC load line. 3. With a neat sketch, clearly show the various current components in a PNP transistor and hence establish the relevant equations.
4. Sketch and explain the current components in transistor. Hence define emitter efficiency, transport factor and large signal current gain. 5. What are the three regions of operation of a BJT? What are the biasing conditions for each of these regions? Mention the region in which BJT acts as an amplifier. 6. Clearly explain the effect of temperature and (Beta) on the operating point stability. 7. Discuss the causes of bias instability in transistor. 8. Sketch and explain the current components crossing each junction of a transistor biased in the active region. 9. A transistor is capable of providing amplification. Explain the basic transistor amplifier with suitable diagrams. 10. Bring out the relationship between (Alpha) (Beta) of transistor. 11. Draw the transistor circuit in CB configuration. Sketch the output characteristics. Indicate active, saturation and cutoff region. Brief explain the nature of those curves. 12.For a transistor working in CB configuration, explain the input and output suitable diagrams. characteristics with a 13.Sketch and explain the input and output characteristics of a transistor in CE configuration on the output characteristics. Clearly indicate the 3 operating regions and mention the biasing requirement for each. 14. Compare amongst CC, CB, CE configurations of a transistor amplifier in terms of the current gain, the voltage gain, and the input impedance and output impedance. 15. Draw a fixed bias circuit and explain why the circuit is unsatisfactory if the transistor is replaced by another of the same type. Derive an expression for its stability factor. 16. Draw the sketch of the output characteristics of a transistor in common emitter configuration? Indicate various region operation and comment for the shape of characteristics qualitatively. 17. Discuss the causes of instability in a transistor.
MODULE-2: BJT BIASING & INTRODUCTION TO OPERATIONAL AMPLIFIERS BIASING METHODS 1. Explain the concept of Load line in case of transistors and thus discuss the biasing techniques applied to NPN transistors. 2. What do you mean by stabilization? 3. Define stability factor? Find the relationship between stability factor and I b? What is its ideal value? 4. Give the essential requirements of stabilization. 5. Derive the stability factor for the feedback resistor circuit. 6. Find the stability factor S for self-biasing circuit? 7. Find the stability factor S for Voltage divider bias circuit 8. Find the stability factor S for fixed bias circuit. 9. Define Operating point. Explain why Operating point should be stable. 10. Determine the operating point for the fixed bias circuit for the following given parameters V CC =12 volts, R B =240K, R C =2.2K, Beta=50 11. Determine the operating point for the feedback resistor circuit for the following given parameters V CC =12 volts, R B =240K, R C =2.2K, Beta=100,R E =2.2K 12. Determine the operating point for the voltage divider bias circuit for the following given parameters V CC =12 volts, R E =1.2K, R C =5.6K, Beta=50,R 1 =82K, R 2 =22K 13. Design a voltage divider bias circuit if operating point + 10V,2mA and V CC =18V, neglect V BE 14. For the CE circuit R B between base and supply Vcc is 1.5 Mohm, R C between collector and Vcc is 5 Kohm, Vcc=30volts. Draw the DC load line and mark the dc operating point on it. Assume =100 and neglect V BE. OPERATIONAL AMPLIFIERS 1. Discuss Integrated circuit. Briefly give the classification of digital IC s based on the component fabrication. 2. Draw the block schematic of an op-amp and Explain the function of each stage. 3. What are the applications of op-amp. 4. What are the ideal characteristics of op amp.
5. Define and mention the importance of the following terms w.r.t. an op-amp i) CMRR ii) Slew rate iii) PSSR iv) I/p offset voltage iv) Virtual ground. 6. Define for an op-amp i) CMRR ii) output offset voltage. What are their typical values for a 741 op-amp? 7. Explain the working of op-amp as i) Adder ii) Subtractor iii) Integrator. 8. Derive an expression for output voltage of an op-amp. i) Inverting amplifier ii) ii) Adder iii) iii) Integrator iv) iv) Differentiator 9. Derive the expressions for voltage gain with feedback of i) Inverting op-amp ii) Non-Inverting op-amp 10. Explain how an op-amp can be configured as an adder and an integrator. Obtain the output expression for both. 11. Mention a least of five parameters expected for an operational amplifier. What their ideal expected values? What are their practical values for a 741 op-amp. 12. Explain op-amp as i) Voltage follower ii) Comparator. 13. Design an-adder circuit using an op-amp to obtain an output expression Vo= 2 (0.1 V1 + V2 + 20V3) Where V1, V2 and V3 are inputs. 14. Calculate the output voltage of a three input summing amplifier given: R 1 = 200 Kohm, R 2 =250 Kohm, R 3 =500Kohm, R f =1Mohm, V 1 = -2V, V 2 =+2V, V 3 =+1V.
MODULE 3: DIGITAL ELECTRONICS 1.Explain the conversions with one Example. i)decimal to Binary ii) Binary to decimal iii) Decimal to octal iv) Octal to decimal v) Decimal to Hexadecimal vi) Hexadecimal to decimal 2.Convert i) (284.65) 10 = (?) 8 =(?) 16 ii) (ABFE) 16 =(?) 2 =(?) 10 3. Perform the following i) (57.6) 8 =(?) 2 = (?) 16 ii) (193) 16 =(?) 8 = (?) 10 4. Use 1 s and 2 s compliment to perform i) 1111 1101 ii) 10111 10011 iii) 1101 1001 5. To subtract 101 from 111 use 2 s and 1 s compliment. 6. Add (47) 8 and (FA) 16 7. Subtract F2A from 3BC and Vice versa.use 2 s Compliment method. DIGITAL LOGIC 1. State and prove De-Morgan s theorem for two variables. 2. Write the symbol, truth table and output expression for i) OR gate ii) NAND gate iii) EX-OR gate iv) NOR gate v) AND gate vi) NOT gate. 3. Draw and Explain the circuit of current mode logic that works as an OR gate. 4. Realize an OR logic gate using diodes. 5. Explain the operation of NOT gate using a transistor. 6. Realize Ex-OR gate using NOT, OR and AND gates only. 7. Realize an AND logic gate using diodes. 8. Draw the logic circuit of full adder. Write Truth table and expression for a 3 input full adder. 9. Write the truth table of a full adder and explain how it can be constructed using half adders. 10. Draw the circuit of full adder and write its truth table..
MODULE -4: FLIP-FLOPS & MICROCONTROLLER 8085 1. Show the logic diagram of a clocked RS flip flop with truth table. 2.Show the logic diagram of a clocked D flip flop with truth table. 3. Show the logic diagram of a clocked JK flip flop with truth table. 4. Show the logic diagram of a master slave flip flop with truth table. 6. Draw the architecture of a microcontroller and explain the each. Microcontroller. 1. Mention the features of µc 8051 and explain the memory division of internal RAM 5. Draw the architecture of 8051 and explain the functions of each block 6. Draw the block diagram of MC 8051 interfacing with stepper motor & explain its working 7. Mention the functions of Accumulator, ALU, and Program counter and stack pointer MODULE-5: COMMUNICATION SYSTEMS & TRANSDUCERS 1. Explain the need for modulation in Communication systems. 2. With a block diagram, explain the important feature of a communication system. 3. Draw the block diagram of Super hetrodyne receiver and explain the function of each stage with necessary waveform. 4. Define i) Modulation ii) Amplitude modulation iii) Frequency modulation iv) Phase modulation v) Modulation index 5. Define AM and derive the necessary expression for AM. 6. What is amplitude modulation? Derive the Expressions for (a) Modulation index, (b) Transmitted power in terms of carrier power and modulation index. 7. Explain with the waveforms the principal of amplitude modulation. Write the expression for AM wave. 8. For an AM wave, derive the expressions for modulation index and total power contained in AM wave. 9. Obtain an expression for the total output power of the amplitude double side band signal.
10. Explain the principle of frequency modulation. Draw the frequency spectrum of FM wave. 11. What are the advantages of FM system over AM system? Make a critical comparison. 12. Bring out the merits and demerits of AM and FM. 13.A carrier of 1 MHz with 400 watts of its power is amplitude modulated with a sinusoidal signal of 2500 Hz. The depth of modulation is 75%. Calculate the sideband frequencies, the band width, the power in the side bands and the total power in the modulated wave. 15. The total power content of an AM wave is 2.64 Kwatts at a Modulation factor of 80%. Determine the power content of i) Carrier ii) each side band. 16. A 500 watts 1 MHz carrier is amplitude modulated with a sinusoidal signal of 1kHz. The depth of modulation is 60%. Calculate the band width, power in the side bands and the total power transmitted. 17. A carrier signal has a peak amplitude of 1000 volts. Modulation index is 40%. Power is developed across a load of 100 Ohm. Determine the value of transmitted power. 18. A 100 MHz carrier wave is frequency modulated by a 10 KHz sinusoidal modulating signals. If the maximum frequency deviation is 50KHz. find the modulation index. Transducers 1. Define a transducer and list its advantages. 2. Explain electrical transducers and different types of electrical transducers. 3. What is the difference between a passive transducer and a active transducer. 4. Explain with diagram the functions of a resistive transducer 5. Describe with the help of a diagram the construction of a LVDT. 6. Explain thermistor. 7. Describe with a diagram the operation of a piezo-electric transducer.