Code: D-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. The quiescent point (Q) is selected in the middle of the active region because 

(A)  it gives better stability.                   (B)  the circuit needs a small voltage.

(C)   it gives distortion less output.        (D)  it is easy to select.

b. FET is a

(A) unipolar transistor                         (B)  bipolar transistor

(C)  tripolar transistor                          (D)  can be both unipolar and bipolar

             c.   If the transistor amplifier draws 20 micro-amp when the input signal voltage is 10 mV, then the input impedance is

(A) 200 ohm.                                     (B)  2 ohm.

(C)  5 ohm.                                         (D)  500 ohm.

             d.   For amplification of very low frequency (<10 Hz)signal, the most appropriate amplifier is

(A)  RC coupled amplifier.                 

(B)  transformer coupled amplifier.

(C)  Direct coupled amplifer.

(D)  first stage capacitance coupled and second stage transformer coupled.          

             e.   The maximum efficiency  of class B amplifier is

(A) 50%                                            (B)  78.5%

(C)  25%                                             (D)  100%

             f.    The negative feedback in an amplifier is to

(A) increase the noise                         (B)  decrease harmonic distortion

(C)  increase the voltage gain               (D)  increase the bandwidth

             g.   The loop gain of the oscillator to start with is

(A) Slightly more than one.                 (B)  More than 100.

(C)  Less than one.                              (D)  Zero. 

             h.   An amplifier of pass band 400 KHz to 420 KHz will be named as

(A) Video amplifier.                            (B) Audio amplifier.

(C) Tuned voltage amplifier.                 (D) Power amplifier.

             i.    A bistable circuit has

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

(C) Two stable states.                          (D) Zero output each time a positive or

negative signal is applied.

             j.    Input impedance of ideal op-amp is

(A)  Finite                                            (B)  Zero.

(C)  Infinite.                                         (D)  Unity.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Draw the collector to base bias circuit and analyse the stability factor for the circuit.            (8)

             b.   In a CE circuit following quantities are measured

                   (i)   When ac output is short circuited i.e. Vce =0                                                   

     I_b   =15                   I_c= 1.5 mA

                           V_be= 15mv

                   (ii)  When ac input is opened (i.e. I_b =0)

                            V_be = 1mv,  I_c = 90 ,    V_ce =1.5V                                                           

Determine all the h-parameters of the circuit assuming that all values are ac rms.                  (8)

Q.3     a.   Draw the circuit of an RC coupled amplifier and explain its operation.                 (8)

             b.   Draw the circuit diagram of push-pull amplifier and explain its working.               (8)

Q.4     a.   For a power amplifier working in class-A operation, the zero signal collector current is 100mA, if dc supply voltage .  Find                 

(i) the maximum ac power output.

(ii) The power rating of transistor.

(iii) The maximum collector efficiency.                                              (8)

b.   Derive an expression for gain of an amplifier with negative feedback.                   (8)

Q.5     a.   The gain of an amplifier without feedback is 100 where as with the negative feedback it falls to 50.  If due to ageing the amplifier gain without feedback falls to 80, find the percentage reduction in stage gain.    

(i) without feedback.

(ii) with negative feedback.                                                              (8)

     b.   Draw the circuit diagram of a double tuned voltage amplifier and explain its working.                       (8)

  Q.6     a. Draw the circuit diagram of a monostable multivibrator and explain its working.                   (8)

             b.   Explain the operation of an astable multivibrator based on IC 555.                      (8)

Q.7     a.   Explain the operation of FET as an amplifier. State its advantages and disadvantages.                      (8)

b.   Draw the circuit diagram of Wien Bridge oscillator and explain its working.                         (8)

Q.8     a.   In the RC network of a Wien Bridge oscillator R1=R2=220 . Determine the value of each of the gang capacitor to obtain a frequency of 3 KHz at the output.                                                      (8)

             b.   Draw the circuit diagram of sample and hold circuit and explain its operation.                      (8)

Q.9     a.   An operational amplifier is to have a voltage gain of 50.  Find the required values for the external resistors R1 and R2 for its operation as:

(i) a non inverting amplifier.

(ii) an inverting amplifier.                                                                             (8)

b.   Explain following terms for op-amps:

(i) Slew rate.

(ii) CMRR.                                                                                                 (8)