DipIETE – CS (OLD SCHEME)

 

Code: DC02                                                   Subject: FUNDAMENTALS OF ELECTRONICS

Flowchart: Alternate Process: DECEMBER 2009Time: 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 the best alternative in the following:                                  (210)

 

a.       If the colour code on the body of the resistor given is green, blue and orange with no colour band for the tolerance value, then the value of the resistance is

 

                   (A)    10%                           (B)    10%

(C)      20%.                          (D)    5%

       

b.      A constant-current source has

 

(A)    zero internal resistance                  (B)  high internal resistance

(C) approximately zero resistance        (D)  infinite internal resistance

            

             c.   The donor type impurities

                  

(A)    create excess holes                      

(B)    can be added to germanium but not to silicon

(C) must have only five valance electrons  

(D) must have only three valance electrons

 

             d.   The life time of typical is

 

(A)   100 hours                                    (B)  300 hours      

(C) 100,000+ hours                            (D)  10000 hours  

 

             e.   A transistor is connected in C-E configuration.  If alpha for the transistor is 0.996, than the collector current with no base current and an  of one microampere will be

                  

(A)                                              (B) 

(C)  25mA                                          (D)  2 mA


 

             f.    The voltage gain of an amplifier without feedback is 400. With negative feedback introduced for the above amplifier, its gain for a feedback factor of 0.1 will be

 

(A)    1                                                  (B)  8.5

(C)  9.76                                             (D)  5.25

 

             g.   The Boolean expression Y for the logic circuit shown in Fig.1 below is

 
 

 

 

 


                   (A)             

                   (B) 

                   (C)             

                   (D)

 

 

             h.   A TTL logic gate draws 2mA when its output is HIGH and 3.5 mA when its output is LOW.  If the supply voltage is 5V, than the average power dissipation for the gate is

 

(A)     9.5 W                                          (B)  13.7 mW

(C)  13.7                                       (D)  12.5 pw

 

             i.    An ideal OPAMP has

 

(A)  infinite                                    (B)  infinite

                   (C)  zero                                       (D)  all the above features

 

             j     Integrated circuits are generally made of

 

(A)  Germanium                                   (B) Indium

(C) Gallium                                          (D) Silicon

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.   Which are the most commonly used passive circuit components?  Write three points on each one of them.                                                              (1+9)

 

             b.   A dc voltage source generating 500 V has an internal resistance of .  Find the load current if the load resistance is

                   (i)                                                (ii)                                                (6)          

 

  Q.3     a.   Give the definition of a semiconductor in terms of energy bands.  Write the energy band diagram for an intrinsic semiconductor.                        (5)                                                             

 

             b.  What is a PN junction? Define the quantity static forward resistance for a PN-junction.  Explain how this quantity can be obtained using the V-I characteristics for the junction.  What do you mean by static reverse resistance of the junction?                                                                                  (7)

 

             c.   Suggest ‘FOUR’ applications for a PN-junction.                                                (4)

 

  Q.4     a.   Write the graphic symbols for the conventional semiconductor diode and the Zener-diode indicating the conduction direction.  Comment on the complete equivalent circuit of the Zener diode in the Zener region and the approximate equivalent circuit.                                                                     (6)

            

             b.   Define the term “electro luminescence”.  Illustrate the process of electroluminescence in the LED by a neat sketch, write the graphic symbol for an LED.                                                                     (4)

 

             c.   Write a note on varactor diodes.                                                                        (6)

 

  Q.5     a.   Explain the basic operation of a BJT using a PNP transistor for illustration.          (9)

 

             b.   Write the equation for the collector current of a transistor in terms of  and  with usual notations.  Comment on the magnitude of the collector current as per the above equation when the transistor is at cut-off and when the transistor is in the active region.                                                     (5)

 

             c.   Rearrange the collector current equation of part (b) to write the collector current equation for a Common-Emitter transistor circuit.                       (2)

 

  Q.6     a.   What are the improvements obtained in an amplifier with negative feedback introduced?  Write the schematic of a current-shunt feedback amplifier.                                                                 (8)

 

             b.   An amplifier has a voltage gain of 1000.  With negative feedback, if the voltage gain reduces to 10 what is the fraction of the output that is fed back to the amplifier’s input?                        (3)

 

c.       The specifications of a certain enhancement-type MOSFET are:

                  

                   Is this a P-channel or an N-channel device?  Compute the value of the drain current when .                                                                                                                         (5)

 

  Q.7     a.   Write the following laws of Boolean algebra and mention their use:

                  

                   (i)   Commutative laws.               (ii)  Distributive Laws.                                      (6)

 

b.    Write the circuit symbol and the truth table for the following logic gates

 

(i)                  A 3-input OR gate

(ii)                Exclusive OR gate                                                                      (6)

       

            c.     Write the procedure to convert a non-standard SOP Boolean expression into a standard SOP form.  Convert the Boolean expression  to a standard SOP form. (4)

 

Q.8       a.   What is the advantage of Karnaugh map?  A Karnaugh map is shown below.  Write the logical equation in the standard SOP form.                                                                                     (5)

 

00

01

11

10

00

1

 

1

 

01

 

1

 

1

11

 

1

1

 

10

 

 

1

 

AB

 
                                                                                                                                                                                                                                                                                                                                          

 

CD

 
 

 

 

 

 

 

 

 


             b.   A four-variable logic function is given by,

                   Minimise the above function using K-map.  Indicate the minimisation steps.        (7)

 

             c.   Name the different transistor logic families that you are aware of.  Distinguish between saturated and non saturated logic circuits.                                                                                       (4)

 

Q.9       a.  Why are MOSFETS popular in logic circuits fabrication?  Distinguish between PMOS and NMOS logic circuits.  What is the advantage of CMOS logic?  Write the circuit of a MOS inverter with enhancement load.                                                                                                                  (7)

       

             b.  Why OPAMPS have become popular in electronic system design?  When do you say that an OPAMP is in open-loop condition?  Write the circuit of the basic non-inverting amplifier and the equation for its voltage gain.                                                                                                                  (5)

 

             c.   Indicate two advantages and two disadvantages of monolithic integrated circuits. (4)