RR
Code No: RR102306
Time: 3 hours
I B.Tech (RR) Supplementary Examinations, June 2009 ELECTRICAL AND ELECTRONICS ENGINEERING (Bio-Technology) Answer any FIVE Questions All Questions carry equal marks ?????
Max Marks: 80
1. (a) Explain what do you understand by i. unidirectional current ii. alternating current iii. sinusoidal A.C. current. (b) Define the terms i. R.M.S value ii. time period iii. frequency iv. average value. (c) Find out average value and root mean square value of output waveform of full wave rectifier circuit. Assume the waveform has maximum voltage of 24V with 100Hz frequency. [3+5+8] 2. (a) Discuss the construction of various types of 3-phase induction motor. (b) Explain the terms i. Synchronous speed ii. slip (c) A 4-pole 3-phase induction motor operates from 440V, 3-phase 50 Hz supply and runs at a speed of 1440 r.p.m, What are the values of synchronous speed, slip speed and percentage slip?[6+4+6] 3. (a) Explain how a P-type semiconductor is formed. What are the different impurities used for this process. (b) Derive the expression for intrinsic conductivity.? (c) Explain about charge densities in a semiconductor. [7+4+5] 4. (a) Draw the circuit diagram of half wave rectifier and explain its operation. (b) A half wave rectifier is fed by 220 V, 50 Hz via a step down transformer of turns ratio 11:1 find i. the output DC and [8+8] ii. peak inverse voltage under no load condition. 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) Draw the h-parameter small signal low-frequency BJT model and what are the dimensions of each parameter. (b) Draw the approximate h-parameter model for common collector configuration and derive expressions for current gain, Input Resistance, voltage gain and output resistance. [6+10] 7. (a) Draw the circuit diagram of Wien bridge oscillator using BJT. Show that the gain of the amplifier must be at least 3 for the oscillations to occur. (b) For the fixed-bias Ge transistor, n-p-n type, the junction voltages at saturation and cutoff one in active region, may be assumed to zero. This circuit operate properly over the temperature range -50 o C to 75 o C and to just start malfunctioning at these extremes. The various circuit specifications are: VCC = 4.5V, VBB = 3volts, hf e =40 at -50 o C, and hf e =60 at 75 o C, ICBO = 4 µA at 25 o C and doubles every 10 o C. Collector current is 10 µA. Design the values of Rc1 , R1 and R2 . [8+8] 8. (a) Explain the principle of Half-adder. Draw various implementations of sum and carry of Halfadder. (b) Implement AND and OR gate using discrete components. (c) How do you convert JK-flip-flop to T and D flip-flops. . [6+6+4] ?????