Code: DC-02                                                  Subject: FUNDAMENTALS OF ELECTRONICS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. The colour code of a 1 k  resistance is 

(A)  black, brown, red.                        (B)  red, brown, brown.

(C)  brown, black, red.                        (D)  black, black, red.

b. A constant current source supplies a current of 300 mA to a load of 1 k , when the load is changed to 100 , the load current will be

(A) 3A.                                              (B)  300 mA.

(C)  30 mA.                                        (D)  100 mA.

             c.   A piece of copper and another of germanium are cooled from room temperature to  K. The resistance of

(A) each of them increases.                

(B) each of them decreases.

(C) copper increases and germanium decreases.

(D) copper decreases and germanium increases.

             d.   When a reverse bias is applied to a P-N junction, the width of the depletion layer

(A) remains the same.                         (B) is increased.    

(C) is decreased.                                (D)  may increase or decrease.      

             e.   The transistor configuration producing highest output resistance is

(A) common collector.                        (B)  common base.

(C)  common emitter.                           (D)  common source.

             f.    MOSFET has input impedance of around

(A) 100 M.                                    (B)  1.

(C)  10.                                           (D)  0.

             g.   The truth table shown is one of the four units.

A	B	Y
0	0	1
0	1	0
1	0	0
1	1	1

(A) NAND                                        (B)  NOR

(C)  EXCLUSIVE NOR                     (D)  Exclusive OR

             h.   Totem pole TTL has an output circuit which is known as

(A) active pull-up                                (B) passive pull-up.

(C)  active pull-down                           (D) passive poll-down.

             i.    If the differential and common mode gains of a differential amplifier are 50 and 0.2 respectively, then the CMRR will be

(A) 10.                                               (B) 49.8

(C) 50.2                                              (D) 250

             j.    Ultraviolet radiation is used in IC fabrication process for

(A)  diffusion.                                      (B)  masking.

(C)  isolation.                                       (D)  metalisation.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Explain the colour code of resistors. What do you understand by tolerance in resistors? A resistor has a colour band sequence: gray, blue, orange and gold. What is the range in which the value must be so as to satisfy the manufacturer tolerance?                                                                      (8)

             b.   State and illustrate with the help of an example Thevenin’s theoram.                    (8)

Q.3     a.   Explain the existence of the various electron energy bands in solids. Based on these bands distinguish between insulators, conductors and semiconductors.                                                          (8)

             b.   Explain how a P-N junction is used as a diode.                                                   (8)

Q.4     a.   With the help of a neat diagram explain the constructional features of a zener diode. Also, draw and explain the volt-ampere characteristics of a zener diode. Distinguish between avalanche and zener break down.                                                           (8)

b.   What is varactor diode? Why is it sometimes called the voltage variable capacitor? Explain its operation. Give its applications.                            (8)

Q.5     a.   What are various transistor circuit configurations? Discuss the operation and characteristics of CB configuration.                                       (8)

     b.   The reverse saturation current of an N-P-N transistor in common base circuit is 12.5 A. For an emitter current of 2mA, collector current is 1.97 mA, determine the current gain and base current.  (8)

  Q.6     a.  Draw the symbol and characteristics of an N-channel JFET and mark linear region, saturation region and breakdown region.                               (8)

b.   When drain source voltage is changed by 1.5 volts, the change in drain current  

       is of 120 A, the gate source voltage remaining unchanged. Determine the ac

      drain resistance of the JFET.                                                                             (8)

Q.7      a.  Simplify the expression AB+A(B+C)+B(B+C) using Boolean Algebra 

techniques.                                                                                            (8)

             b. Reduce the following four variable function to its minimum sum of product 

                 form.          

(8)

Q.8   a.  Give a brief account of characteristics of standard TTL series of digital integrated 

circuits.                                                                                                               (8)

           b. Explain Noise margin, fan out, fan in, sourcing and sinking characteristics of a  

               standard TTL gate.                                                                                              (8)

Q.9        Write explanatory notes on ANY TWO:                                                                           

(i) IC packaging Methods.

(ii) Offset currents and Slew rate of an op amp.

(iii) MOSFET NAND gate.

(iv) RC oscillators.                                                                     (8+8)