Bjt Amplifiers And Oscillators(Engineering > Electronics And Communication Engineering ) Questions and Answers

Question 1.  A transistor with hie = 1.5 K and hie = 75 is used in an emitter follower circuit where R1 and R2 are used for normal biasing. Approximate value of its current amplification is
  1.    75
  2.    76
  3.    75/76
  4.    ?75
Explanation:-
Answer: Option B. -> 76
Question 2.  A certain percentage of negative feedback does not yield a fixed reduction in gain because it depends on
  1.    transistor configuration
  2.    ambient temperature
  3.    initial value of gain
  4.    leakage current of the transistor
Explanation:-
Answer: Option C. -> initial value of gain
Question 3.  If the feedback factor of an amplifier is 0.1 and gain without feedback is 40, then its gain with feedback is
  1.    8
  2.    ?l3.3
  3.    10
  4.    200
Explanation:-
Answer: Option A. -> 8
Question 4.   In an audio amplifier, audio signals become garbled and hence difficult to understand when ac input current is large enough to drive the output to
  1.    saturation only
  2.    cut-off only
  3.    either saturation or cut-off
  4.    a value off the load line
Explanation:-
Answer: Option C. -> either saturation or cut-off
Question 5.  An amplifier has a bandwidth of 20 kHz and a midband gain of 50 without feedback. If a negative feedback of 1% is applied, than bandwidth with feedback is ?kHz.
  1.    13.3
  2.    30
  3.    10
  4.    40
Explanation:-
Answer: Option B. -> 30
Question 6.  Regarding improvements obtained by using negative voltage feedback which statement is false?
  1.    increased gain stability
  2.    increased bandwidth
  3.    increased noise
  4.    decreased distortion
Explanation:-
Answer: Option C. -> increased noise
Question 7.  An amplifier without feedback has a distortion of 15% and gain of 40. When 10% negative feedback is applied, the distortion will become ?percent.
  1.    50
  2.    ?45
  3.    3
  4.    ?5
Explanation:-
Answer: Option C. -> 3
Question 8.  A CE amplifier is characterised by
  1.    low voltage gain
  2.    moderate power gain
  3.    signal phase reversal
  4.    very high outupt impedance
Explanation:-
Answer: Option C. -> signal phase reversal
Question 9.   In a CC amplifier, voltage gain
  1.    cannot qceed unity
  2.    depends on output impedance
  3.    is dependent on input signal
  4.    is always constant
Explanation:-
Answer: Option A. -> cannot qceed unity
Question 10. . A transistor amplifier with 85% efficiency is likely to be class ?
  1.    A
  2.    B
  3.    C
  4.    AB
Explanation:-
Answer: Option C. -> C
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