Code: D-08                                                                           Subject: ANALOG 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. The transistor is said to be in Q-state, when

(A)  no signal is applied to it.               

                   (B)  it is unbiased.

(C)   no current is flowing.                   

(D) emitter-base junction is just equal to the collector-base junction.

             b.   If 3 identical amplifier stages with  are cascaded, then effective  is

(A) 40 dB.                                         (B)  100 dB.

(C)  120 dB.                                       (D)  60 dB.

             c.   The MOSFETs have lower turn-off time and they can be operated at higher frequencies when compared to BJTs, because

(A)  The minority carrier storage time is absent in MOSFETs.      

(B)  MOSFETs have higher input impedance.

(C)  MOSFETs are voltage controlled.    

(D)  MOSFETs have positive temperature coefficient.

             d.   In Push-Pull Power amplifiers, usually biasing is not required, because

(A)  dc battery  is employed.      

(B) power transistors do not require biasing.

(C)  heat sinks is used with the transistors. 

(D)  transistors are working in class-B operation.

             e.   The circuit shown in Fig.1 is

(A) Schmitt Trigger.                            (B)  Zero Crossing Detector.

(C)  Time Marker Generator.               (D)  Window Detector.

             f.    An oscillator circuit, which employs both positive and negative feedback is

(A) Hartley Oscillator.                        (B)  Colpitts Oscillator.

(C)  R-C Phase Shift Oscillator.           (D)  Wein-Bridge Oscillator.         

             g.   The circuit shown in Fig.2 is

(A) Shunt Clipper Circuit.                   (B)  Series Clipping Circuit.

(C)  Series Biased Clipping Circuit.      (D)  Shunt Biased Clipping Circuit.

             h.   The overall voltage gain of Darlington emitter follower is

(A) unity.                                            (B)  slightly greater than unity.

(C)  zero.                                            (D)  slightly less than unity.

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2     a.   What is self-bias?  Draw a self-bias circuit. Explain qualitatively from the stability point of view, why the self-bias circuit is an improvement over the fixed-bias circuit.                                                     (7)

             b.   Design a dc bias circuit for an amplifier circuit shown in Fig.3 using an npn silicon transistor.  Given that the transistor has a current gain of 150 at a collector current of 1mA.  The supply voltage for the present circuit is 16V.                                                                                                              (7)

Q.3     a.   (i)  Draw the Hybrid-equivalent circuit for a CE-transistor amplifier at high frequencies and explain the significance of the different components used there in.                                                         (6)

(ii)  Define  and  .  What is the relationship between  and ?                (3)

b.   A CE amplifier has the following h-parameters

,          

                   If both the load and source resistances are 1 K, then find

                   (i)  Voltage gain                                   (ii)  Current gain.                                     (5)

Q.4     a.   Sketch the small-signal, high frequency equivalent circuit of a CS-FET amplifier and derive an expression for the voltage gain and input admittance.                                                               (10)

             b.   What specific capacitance has the greatest effect on the high-frequency response of cascaded FET amplifier?  Explain.                                               (4)

Q.5     a.   Briefly describe the operation of a class-B Push-Pull power amplifier.  In what respect, it is better than class-A Power amplifier?  What is the major drawback of class-B operation?                             (8)

b.   A class-B Power amplifier is shown in Fig.4.  Calculate

                   (i)  Input Power                        (ii)  Output Power

(iii) Circuit efficiency for an input of 12V, rms.                                          (6)          

  Q.6     a.   Give the Schematic diagram of construction of an N-channel Depletion type MOSFET and explain its operation.                                            (7)

             b.   Sketch a neat circuit diagram of a Transformerless audio Power amplifier and explain its working principle.                                                            (7)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7     a.   What is a Band Pass Filter.  Draw a circuit of a First Order Wide Band-Pass Filter and explain its operation.                                                                                                                         (7)

b.   Design a First Order Wide Band-Pass Filter having  and Pass band gain of H.  Find the value of Q of the filter.                                                                          (7)

Q.8     a.   State Barkhausen criterion for sustained oscillations and how does a oscillator differ from an amplifier as far as circuit configuration is concerned?                                                                  (3)

             b.   Sketch the circuit of a RC phase shift oscillator using BJT and explain its principle of operation.  Derive an expression for the frequency of oscillations.                                                                        (11)

Q.9     a.   A Biased combination clipper is shown in Fig.5.  Determine the output waveform by labelling the voltages for sinusoidal input signal waveform.          (3)

             b.   Draw the circuit diagram of a Positive clamper using diode and explain its operation when the input waveform is a 40V(Peak to  Peak) sinusoidal signal.                                                          (4)

             c.   Draw the functional diagram of a Monostable multivibrator using 555-IC and explain its operation.                                                             (7)

Q.10           a.                                                        Draw the circuit of Schmitt trigger using Op-amp and explain its operation with the help of input and output waveforms.                                       (7)

             b.   Explain the operation of Unijunction oscillator using UJT and find an expression for the frequency of oscillations.  Draw the output waveforms.                                                           (7)

Q.11                                                                      Write short notes on any TWO of the following :

(i) Triangular Wave Generator using Op-amp.

(ii) Sample and Hold Circuit.

(iii) Darlington Emitter follower.                                                                (7 x 2)