Code: DE-08                                                                         Subject: ANALOG 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. For faithful amplification with germanium transistor, the base emitter junction voltage V_BE should not fall below

(A)  0.3 V.                                          (B)  0.5 V.

(C) 0.7 V.                                         (D)  0.1 V.                                                           

             b.   If a transistor amplifier draws  when the input signal voltage is 10 mV, then the input impedance is 

(A) .                                         (B) .

(C) .                                             (D) .

             c.   The minimum gain requirement of an RC phase shift oscillator is

(A) 3.                                                 (B)  29.

(C)  unity.                                            (D)  infinity.

             d.   The maximum efficiency of class A amplifier is

(A) 50%.                                            (B) 78.5%.

(C) 35%.                                            (D) 100%.

             e.   The voltage gain of an amplifier is 100; When negative feedback with m=0.04 is introduced, its gain will be 

(A) 20.                                               (B)  25.

(C)  4.                                                 (D)  0.4.

             f.    The negative feedback in an amplifier

(A) Increase the voltage gain.              (B)  Decrease harmonic distortion.

(C)  Stabilises the voltage gain.             (D)  B & C.

             g.   The most important characteristic of a crystal oscillator is

(A) Its high efficiency.                        

(B) That it requires low d.c. supply.

(C) That its output frequency is stable.     

(D) It has low cost.                            

             h.   A sample and hold ckt is used in

(A) feedback amplifier.                       (B)  oscillators.

(B) DAC.                                           (D)  ADC.

             i.    A bistable multivibrator has

(A) No state stable.                            (B) One stable state.

(C) Two stable states.                          (D) None.

             j.    An integrator is a

(A)  High pass filter.                             (B)  Low pass filter.

(C)  Band pass filter.                            (D)  None.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Draw and explain the fixed bias circuit and analyse for stability.                           (8)

             b.   A  CE amplifier has following h parameters

                   If the load and source resistance are 1  each.  Find current and voltage gain.                (8)

Q.3     a.   Draw the circuit diagram of R.C. coupled transistor amplifier.  Explain its frequency response.                                                                    (8)

             b.   Obtain an expression for the gain of an amplifier with feedback.  State the advantages of negative feedback.                                                                                                                         (8)

Q.4     a.   The gain of the amplifier is 100 with its bandwidth of 10 kHz.  If 10% of negative feedback is applied in the basic amplifier,  determine the feedback gain and new bandwidth of the amplifier. (8)

b.   Draw and explain the circuit of complementary push pull amplifier.                      (8)

Q.5     a.    Discuss harmonic distortion in power amplifiers.                                                 (8)

     b.   For a power amplifier working in class A operation, the zero signal collector current is 100 mA.  If d.c. supply voltage .  Determine

(i) Maximum a.c. power output.

(ii) The power rating of transistor.

(iii) Maximum collector efficiency.                                                    (8)

Q.6     a. Draw the circuit diagram of bistable multivibrator and explain its working with suitable waveform.                                                               (8)

             b.   In a phase shift oscillator, each resistor in RC network is 10 KW while each capacitor has a value of .  Find the operating frequency of the circuit.  What is the phase shift produced by each RC section.  Comment on results.                                                                                          (8)

Q.7     a.   Explain the operation of integrator and differentiator using OPAMP.                    (8)

b.   Draw the circuit diagram of logarithmic amplifier and explain its working.             (8)

Q.8     a.   Draw the circuit diagram of Colpitt’s oscillator and explain its working.               (8)

             b.   Draw the circuit diagram of double tuned amplifier and explain briefly.                 (8)

Q.9     a.   Draw and explain the circuit diagram of Schmitt trigger with suitable waveforms      .           (8)

b.   Explain the operation of astable multivibrator using 555 timer.                             (8)