Rr12302-electrical-and-electronics-engineering

Set No. 1

Code No: RR12302

I B.Tech Supplimentary Examinations, Aug/Sep 2008 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) A voltage wave form shown in the figure 1a is applied to a pure resistance of 40 Ω. Sketch the wave form of the current passing through the resistance.

Figure 1a (b) Solve the network shown in the figure 1b below for currents in the various resistors. [6+10]

Figure 1b 2. (a) Explain the constructional details of a synchronous machine giving the reasons for making two types of rotors. (b) Explain auxiliary motor starting of synchronous motors.

[6+10]

3. (a) For the network shown in the figure 3(a)i determine the range of RL and IL that will result in VRL being maintained at 10 V. 1 of 3

Set No. 1

Code No: RR12302

i. Determine the maximum Wattage rating of the diode.

Figure 3(a)i ii. The reverse saturation current of the diode is 1 µA. Its peak inverse Voltage is 500V. Find ri , Vo that PIV is not exceeded. show in figure 3(a)ii & figure 3(a)ii

Figure 3(a)ii

Figure 3(a)ii 2 of 3

Set No. 1

Code No: RR12302

4. (a) What do you mean by regulation and explain how a full wave rectifier is used for it. (b) Compare center tapped transformer and ordinary transformer. What is the difference in their construction? (c) Mention the applications of rectifiers in detail.

[6+5+5]

5. (a) Define different stability factors of biasing circuits using BJT. (b) List out different transistor biasing methods and compare their merits and demerits. (c) Write short notes on i. Thermal runaway ii. Early effect

[6+6+4]

6. (a) Draw the circuit diagram of an emitter follower circuit and its h-parameter model. (b) For the given component values Rs = 1KΩ, RL = 3 KΩ and for the given hparameters hf e = 100, hie = 2KΩ, hre = 2.5 × 10−4 , hoe = 10µA/V. Calculate AI , RI , Avs and R0 . [6+10] 7. (a) What kind of feedback is incorporated in the Wien bridge oscillator circuit and why? (b) In a colpitts oscillator using FET, the frequency of oscillations is observed to be 2.5 MHz. Oscillator uses L=10 µH, C1 = 0.02 µF. Find i. the value of C2 ii. If L is doubled the new value of frequency oscillations. (c) Explain about the applications of OP-AMPs.

[4+6+6]

8. (a) Realize NAND gate using minimum number of NOR gates. (b) Explain the principle of basic shift registers. (c) Distinguish between asynchronous and synchronous counters. (d) Distinguish between Ring and Twisted Ring counters. ⋆⋆⋆⋆⋆

3 of 3

[4+4+4+4]

Set No. 2

Code No: RR12302

I B.Tech Supplimentary Examinations, Aug/Sep 2008 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) State and explain Kirchoff’s Law.

[6M]

(b) Calculate the current through the resistance of 5 Ω in the specified direction as shown in the figure 1b [10M]

Figure 1b 2. (a) Explain the process of voltage build up in a self-excited D.C machine. (b) List out the various conditions to be satisfied for voltage build up process in a self-excited machine, and write down remedies if the conditions fail. [8+8] 3. (a) Prove that the Fermi  level  for p-type semiconductor is given by NV EF = EV + KT ln NA . (b) In a p-type semiconductor, if the concentration of acceptor atoms is increased by a factor 10, find the shift in the position of Fermi level. Assume KT=0.03 ev. [10+6] 4. (a) The half wave rectifier shown in the figure 4a is fed with a sinusoidal voltage V=20 sin100t. i. Sketch the output waveform. ii. Determine the DC output voltage assuming ideal diode behaviour. iii. Repeat the calculations assuming the simplified diode (silicon) model.

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Set No. 2

Code No: RR12302

Figure 4a (b) Draw the circuit diagram of full wave rectifier having two diodes and explain its operation. [8+8] 5. (a) Sketch the input and output characteristics of CB configuration for an n-p-n transistor, Explain the shape of the curves qualitatively. (b) For the circuit in figure 5b shown if α = 0.98 VBE = 0.7 V find R1 in the circuit for an emitter current of IE = -2 mA. Neglect the reverse saturation current. [8+8]

Figure 5b 6. (a) Compare the three transistor amplifier configurations with related to AI , Av , Ri and R0 . (b) For the circuit shown calculate AI , AV , Ri and R0 using approximate h-parameter model. Assume hf e = 50, hie = 1100 Ω, hoe = 25 µA/V, hre = 2.5 × 10−4 as shown in the figure 6b. [16]

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Set No. 2

Code No: RR12302

Figure 6b 7. Define the following terms with reference to OP-AMPs: (a) i/p bias current (b) i/p offset current (c) open loop gain (d) i/p off set voltage (e) o/p offset voltage (f) CMRR (g) PSSR (h) Skew rate.

[16]

8. (a) Explain with a block diagram the major blocks of a digital computer. (b) Implement the following with either NAND or NOR gates. Use only 4 gates only the normal inputs are available. F = w′ xz + w′ yz + x′ yz′ + wxy′ z. (c) With a circuit diagram, explain Counter type A to D converter. ⋆⋆⋆⋆⋆

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[4+6+6]

Set No. 3

Code No: RR12302

I B.Tech Supplimentary Examinations, Aug/Sep 2008 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Determine the effective resistance between the nodes A and B in the circuit shown in the figure 1a (all values are in ohms).

Figure 1a (b) Find the Vc and IL from the circuit shown in Figure 1b under steady state conditions. [10+6]

Figure 1b 2. (a) Name the various parts of a D.C machine and give the materials used for each part. Also show the magnetic path. (b) Explain the principle of operation of D.C motor.

[8+8]

3. (a) Prove that the concentration of holes in an intrinsic semiconductor is given by p = Nv e−(EF −EV )/KT . (b) Prove that for intrinsic semiconductor n2i proportional to T 3 e−EGO /KT [6+10] 4. (a) The half wave rectifier shown in the figure 4a is fed with a sinusoidal voltage V=20 sin100t. i. Sketch the output waveform. ii. Determine the DC output voltage assuming ideal diode behaviour. iii. Repeat the calculations assuming the simplified diode (silicon) model.

1 of 3

Set No. 3

Code No: RR12302

Figure 4a (b) Draw the circuit diagram of full wave rectifier having two diodes and explain its operation. [8+8] 5. (a) Compare and contrast FET and BJT. (b) Give the constructional features of JFET and explain its operation with the help of the drain characteristics. (c) From the drain characteristics derive mutual characteristic and explain the shape of the curve qualitatively. [6+6+4] 6. (a) Compare the three transistor amplifier configurations with related to AI , Av , Ri and R0 . (b) For the circuit shown calculate AI , AV , Ri and R0 using approximate h-parameter model. Assume hf e = 50, hie = 1100 Ω, hoe = 25 µA/V, hre = 2.5 × 10−4 as shown in the figure 6b. [16]

Figure 6b 7. (a) Explain the operation of an integrator using OP-AMPs. (b) Distinguish between positive and negative feedbacks. (c) List out the characteristics of OP-AMP. 2 of 3

[6+4+6]

Set No. 3

Code No: RR12302 8. (a) Convert the following numbers: i. (1431)10 to base 2. ii. (53.1575)10 to base 2.

(b) Implement AB+C′ D′ = F with three NAND gates. Draw the logic circuit. (c) Prove that the NAND Gate is a universal gate.. ⋆⋆⋆⋆⋆

3 of 3

[8+4+4]

Set No. 4

Code No: RR12302

I B.Tech Supplimentary Examinations, Aug/Sep 2008 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Determine the effective resistance between the nodes A and B in the circuit shown in the figure 1a (all values are in ohms).

Figure 1a (b) Find the Vc and IL from the circuit shown in Figure 1b under steady state conditions. [10+6]

Figure 1b 2. (a) Describe the construction of a 1-phase transformer and principle of operation. (b) Write about 3-phase transformer connections.

[8+8]

3. (a) For the network shown in the figure 3(a)i determine the range of RL and IL that will result in VRL being maintained at 10 V. i. Determine the maximum Wattage rating of the diode.

1 of 3

Set No. 4

Code No: RR12302

Figure 3(a)i ii. The reverse saturation current of the diode is 1 µA. Its peak inverse Voltage is 500V. Find ri , Vo that PIV is not exceeded. show in figure 3(a)ii & figure 3(a)ii

Figure 3(a)ii

Figure 3(a)ii 4. (a) The half wave rectifier shown in the figure 4a is fed with a sinusoidal voltage 2 of 3

Set No. 4

Code No: RR12302 V=20 sin100t.

i. Sketch the output waveform. ii. Determine the DC output voltage assuming ideal diode behaviour. iii. Repeat the calculations assuming the simplified diode (silicon) model.

Figure 4a (b) Draw the circuit diagram of full wave rectifier having two diodes and explain its operation. [8+8] 5. (a) Draw the emitter characteristic of UJT and explain the shape of the curve qualitatively. Mention different regions of operations. (b) Draw the circuit of a relaxation oscillator and explain its operations. Mention its applications. [8+8] 6. (a) Give the advantages of negative feedback amplifier. (b) Draw the circuit of a voltage shunt feedback amplifier and explain. (c) When the negative feedback is applied to an amplifier of gain 100, the overall gain falls to 50. Calculate i. the feedback factor ‘β’ ii. If the same feedback factor is maintained, find the value of amplifier gain required if the overall gain is to be 75. [4+6+6] 7. (a) List out the characteristics of OP-AMPs. (b) Explain about the concept of ‘Virtual Ground’ in OP-AMPs. (c) Draw the circuit diagram of emitter coupled differential amplifier and obtain its DC analysis.. [6+4+6] 8. (a) Realize NAND gate using minimum number of NOR gates. (b) Explain the principle of basic shift registers. (c) Distinguish between asynchronous and synchronous counters. (d) Distinguish between Ring and Twisted Ring counters. ⋆⋆⋆⋆⋆

3 of 3

[4+4+4+4]