Code: DE08                                                                          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. A sample and hold circuit is used in

(A)  feedback amplifier.                       (B)  DAC.

(C)  ADC.                                          (D)  none of the above.                                        

             b.   The largest effect of forward current gain  in CE circuit is on   

(A) the input resistance of the circuit.  

(B) the output resistance of the circuit.

(C) current gain of the circuit.             

(D) unity gain frequency of the circuit.

             c.   In an ideal op-amp, the input impedance is

(A)  zero.                                           (B)  50 .

(C)  100 .                                        (D)  infinite.

             d.   Double tuned amplifiers provide

(A) increased selectivity.                     (B) increased bandwidth.

(C) increase voltage gain.                    (D) none of these. 

             e.   The frequency response of transformer coupling is 

(A) poor.                                           (B)  good.

(C)  excellent.                                      (D)  none.

             f.    Heat sinks are used with power amplifiers to 

(A) increase the collector dissipation rating of the transistor.         

(B) increase the gain of the transistor.

(C) increase the power output.           

(D) none of the above.

             g.   The negative feedback in an amplifier 

(A) increases the voltage gain.             (B)  increases the harmonic distortion.

(C)  stabilizes the voltage gain.             (D)  none of the above.

h.   Inverting amplifier using an op-amp is an example of

(A) voltage series feedback.                (B)  voltage shunt feedback..

(C) current series feedback.                 (D)  current shunt feedback.

             i.    For obtaining frequency response of an amplifier in the lab, we use

(A) a sine wave source.                       (B)  square wave source.

(C) triangular wave source.                  (D) any source.

             j.    If the stages of cascaded amplifier have decibel gains of 60 and 80 then overall gain in dB is

(A)  140.                                             (B)  4800.

(C)  20.                                               (D)  None.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Describe the potential divider biasing circuit.  Explain how stabilization of operating point is achieved.                                                                     (8)

             b.   For the circuit given below, draw the load line and find the operating point.  Assume .                                                               (8)

Q.3     a.   A CE amplifier has following h parameters:

 mho

                   If the load and source resistance are both .  Find current and voltage gain.                   (10)

             b.   Distinguish between voltage and power amplifier.                                                (6)

Q.4     a.   For class A, CE transistor amplifier, the operating point is located at  and .  Due to input signal the output collector current goes in between450 mA and 40 mA.  The  swings between 15V and 1V.  Find

(i) the output power delivered.

(ii) the input power.

(iii) collector efficiency.

(iv) power dissipated by transistor.                                                   (8)

             b.   An Si transistor dissipates 2W during working.  If maximum junction temperature is .  Find

                   (i)  maximum ambient temperature at which it can be operated.(assume )

                   (ii)  If in place of this transistor another equivalent  transistor having is applied, at what temperature it can be operated.            (8)

Q.5     a.   What is total harmonic distortion?  Explain briefly.                                               (8)

     b.   Describe  the effect of negative feedback on noise and output impedance.           (8)

  Q.6     a. Describe inverting & non inverting amplifier using op-amp.                                  (8)

             b.   Explain how an op-amp can be used as logarithmic amplifier.                              (8)

Q.7     a.   An op-amp is to have a voltage gain of 50.  Find the required values for external resistors  and  if (i)  a non inverting (ii)  an inverting gain is required.                                                                  (8)

b.   Design an astable multivibrator using the 555 timer to generate a square wave of 5 kHz with 70% duty cycle.                                                            (8)

Q.8     a.   What do you mean by clipper circuit?  Describe combination clipper circuit.                       (8)

             b.   Describe the operation of monostable multivibrator using 555 timer.                    (8)

Q.9     a.   Describe the operation of RC phase shift oscillator.                                             (8)

b.   Find the operating frequency of transistor Colpitt’s oscillator if  and .                                                              (8)