# JNTU Basic Electronics Exam Paper Apr-May 2008

JNTU B.Tech II Semester Examinations, BASIC ELECTRONICS,  Apr/May 2008

(Metallurgy & Material Technology)

Time: 3 hours Max Marks: 80

All Questions carry equal marks

SET-IV

1. (a) Determine the factor by which the reverse saturation current of a semiconductor diode is multiplied when the temperature is increased from 25o to 85oC.

(b) Explain the operation of Full Wave rectifier with resistance load. Explain the necessity of filters in rectifier circuits. [6+10]

2. (a) Sketch typical output characteristic curves for a PNP transistor in CB configuration. Label all variables and indicate active, cut – off and saturation regions.

(b) Define all important parameters of J F E T.

(c) For a J F ET, the typical values of trans-conductance and amplification factor are 250 ? mho and 100 respectively. Calculate the dynamic drain resistance of this J F E T. [6+6+4]

3. (a) Explain the two transistor analogy of SCR.

(b) Draw the V-I characteristics of TRIAC and explain the principle of working of TRIAC. [6+10]

4. (a) Discuss with mathematical expressions, how the negative feedback in amplifiers reduces the distortion and increases the band width of the amplifier.

(b) Calculate

i. voltage gain

ii. output impedance.

iii. Band width of a feedback amplifier with parameters of the internal amplifier as A=250, Z0=30 k , Bandwidth = 50 kHz and having feedback factor ? =0.02. [8+8]

5. (a) Draw the circuit of Hartley Oscillator using transistor and explain the working of it.

(b) In a transistor Hartley Oscillator, determine the value of capacitor C required in the frequency determining network with L1 = 100 ?H and L2 =1 mH , in order to have frequency of oscillation fo = 1.05 MHz [10+6]

6. (a) Giving relevant diagram, explain Spot Welding process.

(b) Clarify timers according the function. [10+6]

7. (a) Giving basic set up, explain the principle of Induction heating.

(b) Draw and explain piezo electric generator circuit using Hartley oscillator for generation of Ultrasonic waves. [8+8]

8. (a) What is the difference between A-to-D and D-to-A converters?

(b) List 8085 registers and describe its functions. [8+8]