Code: DC-02                                                  Subject: FUNDAMENTALS OF ELECTRONICS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

Q.1       Choose the correct or best alternative in the following:                                           (2x8)

a. In a limited space, the capacity provided by electrolytic capacitors is  

(A) Low.                                             (B) Medium.

(C) Some what medium.                      (D) High.

             b.   In the color code designation for resistors, if the color in the last band on its surface is gold then the tolerance value for the resistor is

(A)  3%.                                             (B)  10%.

(C)  20%.                                            (D)  5%.

             c.   The propagation delay time of commercially available DTL gates are of the order of

(A) 10 to 20 ns.                                  (B)  30 to 80 ns.

(C)  5 to 10 ns.                                    (D)  20 to 25 ns.

             d.   The maximum forward current in the circuit shown in Fig.1 is

(A)  9 mA.                                         

(B)  8 mA.

(C)  9.12 mA.                                    

(D)  9.4 mA.

             e.   The decimal number corresponding to the fourth cell in the third row of a     K-map for four variables is

(A) 10.                                                (B)  14.

(C) 11.                                                (D)  15.

f. Integrated Circuit (IC) was invented by

(A) Barteen.                                        (B) Braiden.

(C) Malvino.                                        (D) Jack Kilby.

             g.   The Schottky diode has become the backbone of Low power Schottky TTL because

(A) It can handle high frequencies.        (B)  It has high PIV rating.

(C) It has low cut-in voltage.                (D)  It has no charge storage.

             h.   For a JFET with a saturation drain current of 8 mA and a pinch-off voltage of –4V, the drain current with a gate-to-source voltage of –1V is  

(A) 2.5 mA.                                       (B)  3 mA.

(C)  4.5 mA.                                       (D)  4 mA.

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2     a.   How is an n-type material created?  Support your answer with a neat illustration.                (7)

             b.   Describe the effect of donor impurities on the energy band.                                 (5)

c.   Define majority and minority carriers.   (2)

Q.3     a.   Define the quantities ‘static’ and ‘dynamic’ resistances for the given diode.  Explain how they can be obtained graphically.                            (7)

b. What is an LED?  Describe the process of electro luminescence in the LED.  Write the graphic symbol for an LED.                                                   (7)

Q.4     a.   Define and describe briefly the following for a BJT:

                   (i)  d.c. alpha                                       (ii)  a.c. alpha.                                         (5)

b.   Establish the relationship between  and  of a BJT.                                     (3)

c.   Explain the basic voltage amplification action of the C-B configuration.                (6)          

Q.5     a.  Which is the logic gate that finds application, where two signals are to be compared in the study of digital circuits?  Write its logic symbol and explain its operation.                                                    (5)

b. When do you say that a Boolean function is in canonical form?  Express the Boolean function, in a sum of minterms.                               (7)

c.   What is a ‘product of sums’ Boolean function?  Give one example.                     (2)                      

  Q.6     a.   How do noise appear in a logic circuit?  Write the circuit of a 3-input DTL NAND gate driving ‘N’ similar gates and briefly explain its operation.   (9)

             b.   MOSFETs have become very popular for logic circuits, why?  Write the circuit of a 2-input NMOS NOR gate and briefly explain.                        (5)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7     a.   What is a voltage source?  When do you say that the source is a constant voltage source?  Give an example for the same.  A lead acid battery fitted in an automobile develops 24V and has an internal resistance of 0.01.  It is used to supply current to head lights, wipers, tape recorder & so on.  If the total load is 100 watts, find

(i)   voltage drop in internal resistance  and

                   (ii)  the terminal voltage.                                                                                     (7)

             b.   Explain the characteristics of a Zener diode.                                                        (4)

c.   A 10 V Zener is connected for voltage regulation as shown in the fig.2.  If the load current is 6 mA, find I and .                                               (3)

Q.8     a.   What is a JFET?  Describe the basic construction of an n-channel JFET with a neat sketch for illustration.                                                              (8)

             b.   The data sheet of an FET lists these typical values:

                   Calculate the drain current for (6)

Q.9     a.   What is the principle on which the simplification of the logical functions with K-map is based?  Illustrate the principle by considering a two-variable map.                                                                     (5)

b.   For the Boolean functions specified, give the K-map and write the minimised expressions.

                   (i)  

                   (ii)  (9)

Q.10           a.                                                        Discuss briefly the following applications of JFET:

(i)  Buffer Amplifier ;                           

                   (ii)  Low Noise Amplifier.                                                                                  (8)

     b.   Draw a practical version of a phase-shift oscillator circuit using JFET, and briefly explain, its operation.                                                                  (6)                                                                        

Q.11           a.                                                        Describe briefly the following for an OPAMP:

(i)    Common-Mode operation.

                   (ii)   Common-Mode rejection.                                                                          (6)

b.   Define CMRR for an OPAMP.  Calculate the CMRR in decibels for the circuit measurements shown in the fig.3                                                     (5)

c.   List the different steps involved in the fabrication of monolithic integrated circuit.                  (3)