Electronic Circuits Mid - I, February - 2012

1.Which of the following amplifier has high power gain
  • CB
  • CE
  • CC
  • both CB and CE
Answer: B
2.The gain of an amplifier with feedback is
  • A/1+Aβ
  • β/1+βa
  • β/1-βa
  • A/1-Aβ
Answer: A
3.Voltage feedback amplifier is a
  • shunt – shunt
  • shunt – series
  • series – series
  • series – shunt
Answer: D
4.Negative feedback in amplifier
  • improves SNR at the input
  • improves SNR at the output
  • Increases distortion
  • None of the above
Answer: B
5.1db corresponds to _________ change in voltage level.
  • 40%
  • 80%
  • 20%
  • 25%
Answer: A
6.An important limitation of a crystal oscillator is
  • its low output
  • its high Q
  • less availability of quartz crystal
  • its high output
Answer: A
7.Which of the following device converts dc power into ac power
  • oscillator
  • amplifier
  • both a and b
  • None
Answer: C
8.The value of negative feedback fraction is always
  • <1
  • >1
  • =1
  • None of the above
Answer: A
9.In a RC phase shift oscillator, each RC section provides a phase shift of
  • 30 degrees
  • 60 degrees
  • 90 degrees
  • 180 degrees
Answer: B
10.With feedback, which of the following reduces.
  • system gain
  • system stability
  • both a and b
  • None
Answer: A
11.According to Miller’s theorem, the feedback capacitance when referred to input side with gain A is
_______________________.
Answer: Cin = C(1-A)
12._________________ amplifier is also called as emitter follower.
Answer: CC
13.The units of hrc are _____________.
Answer: No units, it is constant
14.The phase difference between output and input voltages of a CE amplifier is ________________.
Answer: 180 degrees
15.In an ideal current amplifier, the values of Ri & R0 are _______________________.
Answer: 0,∞
16.The Trans resistance amplifier is also called as ____________________
Answer: Voltage – shunt amplifier (or) series – shunt amplifier
17.Hybrid - π model is also known as ______________ model.
Answer: Giacoletto model
18.Write the expression for voltage gain of CS amplifier interms of gm, rd, RL. ________________
Answer: Av = -(gmrdRL ) / (rd +RL)
19.The frequency of oscillations of a Hartley oscillator is _______________________.
Answer: f= 1/(2πLeqC) where Leq = L1+ L2
20.Write Barkhausen criteria ___________________
Answer: │Aβ│=1 & Φ = 2πn where n=0,1,2…….