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1 Code No: Y0221/R07 Set No. 1 I B.Tech Supplementary Examinations, Apr/May 2013 BASIC ELECTRONIC DEVICES AND CIRCUITS (Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) Explain with a block diagram the major parts of CRT. (b) An electron having a speed V 0 = 10 7 m/sec is injected in the XY plane at an angle of 30 0 to the X axis. A uniform magnetic field parallel to the Y-axis and with flux density B = 5.10 mwb/m 2 exists in the region. Find the position of the electron in the region. Find the position of the electorn in space at t=5 m sec after entering the magnetic field. [8+8] 2. (a) Distinguish between zener and Avalanche breakdown mechanisms. (b) Describe the action of PN junction diode and explain how it acts as a switch. (c) Explain the V-I characteristics of a varactor diode. [6+5+5] 3. (a) Derive the expression for ripple in a π - section filter when used with a half wave rectifier. (b) A full-wave single phase rectifier employs a π-section filter consisting of two 4µF capacitances and a 20H choke. The transformer voltage to the center tap is 300V rms. The load current is 500 ma. Calculate the dc output voltage and the ripple voltage. The resistance of the choke is 200 Ω. [8+8] 4. (a) The reverse saturation current of the Ge transistor is 2µA at room temperature of 25 0 C and increases by a factor of 2 for each temperature increase of 10 0 C. Find the reverse saturation current of the transistor at a temperature of 75 0 C. (b) Explain the working principle of MOSFET in enhancement and depletion modes. [6+10] 5. What is the need for biasing? Explain the types of biasing with neat circuit diagrams? [16] 6. (a) Draw the h-parameter equivalent circuit of a transistor in the CB configuration and explain the significance of each term in circuit. (b) A FET amplifier in the common-source configuration uses a load resistance of 300 KΩ. The ac drain resistance of the device if 100KΩ and the transconductance is 0.5mAV 1. Find the voltage gain of the amplifier? [8+8] 7. (a) An amplifier has a gain of -100 and a distortion of 8%. What is the effect of introducing negative feedback with feedback factor of 0.05? (b) Find A f for a CE stage with an un bypassed emitter resistor. [8+8] 1 of 2

2 Code No: Y0221/R07 Set No (a) Consider the two section RC network shown in figure 8a. Find the V i /V f function, and verify that it is not possible to obtain phase shift with a finite attenuation. Figure 8a (b) State the similarities and differences between series and parallel resonance crystal oscillator circuits. [10+6] 2 of 2

3 Code No: Y0221/R07 Set No. 2 I B.Tech Supplementary Examinations, Apr/May 2013 BASIC ELECTRONIC DEVICES AND CIRCUITS (Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) An electron is moving perpendicular to magnetic field B. Derive the expression for radius R of the trajectory and period of rotation T. (b) Derive the expression for the electro magnetic deflection sensitivity in the CRT. [8+8] 2. (a) Distinguish between zener and Avalanche breakdown mechanisms. (b) Describe the action of PN junction diode and explain how it acts as a switch. (c) Explain the V-I characteristics of a varactor diode. [6+5+5] 3. (a) A Volts (rms) ideal transformer is used with a full wave rectifier circuit with diodes having forward drop of 1 volt. The load is a resistance of 100ohm and a capacitor of 10,000µf is used as a filter across the load resistance. Calculate the dc load current and voltage. (b) Draw the circuit diagram of a bridge rectifier circuit with L-section filter and explain its operation. [8+8] 4. (a) For a small signal JFET i D = f(v GS, V DS ). Obtain expressions for i D and hence define g m, r d and µ. (b) From the definition of g m and r d obtain expression for µ. (c) Forann-channelsiliconFETwitha= cmandn D =10 15 electrons/cm 3. Find the pinch off voltage. [5+5+6] 5. (a) Compare the advantages and disadvantages of biasing schemes. (b) Calculate the quiescent current and voltage of collector to base bias arrangement using the following data: V cc =10V, R b =100KΩ, R c =2KΩ, β=50 and also specify a value of R b so that V ce =7V. [8+8] 6. (a) Draw the hybrid model for a CB transistor and write the input and output equations. (b) Explain how to obtain h ie and h re from the CE input characteristics? [8+8] 7. (a) An amplifier has a gain of -100 and a distortion of 8%. What is the effect of introducing negative feedback with feedback factor of 0.05? (b) Find A f for a CE stage with an un bypassed emitter resistor. [8+8] 1 of 2

4 Code No: Y0221/R07 Set No (a) Find the capacitance of the capacitor used in the RC network employed in the phase shift oscillator, if the frequency of oscillation is 956Hz and R=1M Ω. (b) Show that the amplifier used in the wien-bridge oscillator must have a gain greater than 3 for sustained oscillations. [8+8] 2 of 2

5 Code No: Y0221/R07 Set No. 3 I B.Tech Supplementary Examinations, Apr/May 2013 BASIC ELECTRONIC DEVICES AND CIRCUITS (Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) An electron is moving perpendicular to magnetic field B. Derive the expression for radius R of the trajectory and period of rotation T. (b) Derive the expression for the electro magnetic deflection sensitivity in the CRT. [8+8] 2. (a) Derive the expressions for diffusion capacitance of PN juncion Diode. (b) An ideal Ge p-n junction diode has reverse saturation current of 30 µa at a temperature of C. Find the dynamic resistance for a 0.2V bias: i. in the forward direction ii. in the reverse direction. [8+8] 3. (a) With a neat block diagram explain about Zener shunt regulator? (b) A half wave rectifier has load resistance of 10,000Ω and shunt filter capacitor of 10pF. The applied sinusoidal voltage has amplitude of 20V and frequency of 50 cycles/second. The angle of conduction is Assuming the rectifier to be ideal, calculate cut in angle, d.c.load current, d.c. output voltage and ripple factor. [8+8] 4. (a) A silicon transistor with V BE = 0.7V, α = 0.98 and collector cut-off current of 10 µa is connected as shown in figure 4a. Find: (a) β and I CO 1 of 2 Figure 4a

6 Code No: Y0221/R07 Set No. 3 (b) I C, I E and V CE. (c) Briefly describe some applications of JFET. [10+6] 5. (a) Differentiate bias stabilization and compensation techniques. (b) Design a voltage divider bias network using a supply of 24V, β=110 and I CQ =4µA, V ceq =8V choose V e =V cc /8. [7+9] 6. Find the overall h parameters of the accompanying two stage cascaded amplifier. [16] 7. (a) An amplifier has a gain of -100 and a distortion of 8%. What is the effect of introducing negative feedback with feedback factor of 0.05? (b) Find A f for a CE stage with an un bypassed emitter resistor. [8+8] 8. (a) State the Nyquist criterion for stability. (b) Explain the principle of operation of a wien-bridge oscillator with the help of a neat diagram. Obtain an expression for its frequency of oscillation. [6+10] 2 of 2

7 Code No: Y0221/R07 Set No. 4 I B.Tech Supplementary Examinations, Apr/May 2013 BASIC ELECTRONIC DEVICES AND CIRCUITS (Electrical & Electronics Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) Derive the expression for the magnetic deflection sensitivity in a CRT. (b) Compare electro static and magneto static deflection sensitivities in all respects. [8+8] 2. (a) Determine the resistivity of Germanium: i. in intrinsic condition at K ii. with donor impurity of 1 in 10 7 iii. with acceptor impurity of 1 in 10 8 Given for germanium at room temperature. n i = /cm 3 ; µ p = 1800 cm 2 /V-sec, µ n = 3800 cm 2 /V-sec and number of Germanium atoms/cm 3 = (b) Compare Avalanche and Zener breakdown. [10+6] 3. (a) Derive the expression for the ripple factor of half wave rectifier and full wave rectifier. (b) In a full wave rectifier the required dc voltage is 9V and the diode drop is 0.8V calculate ac rms input voltage required in case of bridge rectifier circuit and centre tapped full wave rectifier circuit. [8+8] 4. (a) Draw the circuit and explain the characteristics of BJT (input and output characteristics) in C.E. configuration. (b) Give the specifications, parameters and typical values of a silicon NPN transistor. [8+8] 5. (a) Show that stability factor may be put in the form S = Ge+G 1+G 2 G e/(1+β)+g 1 +G 2 Where the G s are the conductances. (b) What is heat sink? Why it is used? (c) What is the condition for avoiding thermal runaway problem? [8+4+4] 6. Obtain CE h parameters in terms of CB h parameters. [16] 7. (a) The output impedance may be calculated as the ratio of the open circuit voltage to the short circuit current. Using this method evaluate output resistance with feedback R of for a current-series feedback amplifier. (b) Draw an emitter follower circuit diagram and find the feedback factor and the input resistance with feed back. [8+8] 1 of 2

8 Code No: Y0221/R07 Set No A two stage FET oscillator uses the phase shifting network shown in figure 8. Show that the frequency of oscillation is f =1/2πRC and that the gain must exceed 3. [16] Figure 8 2 of 2

Code No: R Set No. 1

Code No: R Set No. 1 Code No: R05010204 Set No. 1 I B.Tech Supplimentary Examinations, Aug/Sep 2007 ELECTRONIC DEVICES AND CIRCUITS ( Common to Electrical & Electronic Engineering, Electronics & Communication Engineering,