NOTE: Don't think that these bits only will be repeated in second mid.Prepare all units thoroughly and just go through these bits to cross check your knowledge.
ECA
JNTUH OBJECTIVE EXAM
UNIT-5: Feedback amplifiers
SECTION-I: Multiple choice questions
1. Negative feedback in amplifier
[
b ]
(a) Improves SNR at the input (b) improves SNR at
the output (c) Increases distortion (d) None of the above
2. The gain of an
amplifier with feedback is ______.
[ a ]
(a) A/1+Aβ (b) β/1+βa (c) β/1-βa (d) A/1-Aβ
3. In voltage shunt feedback, the input
impedance [ b
]
a. increases b. decreases
c. depends on dc voltage applied d. depends on
frequency of operation
4. Which of the following combination can be
used as a buffer_____ [ c ]
a. CE b. CB c. CC d. All
Section-II: Fill
in the blanks
1. The Trans conductance
amplifier is also called as Series – Series amplifier
(or) Current – Series amplifier
2. In an ideal voltage
amplifier, the values of Ri & R0 are ∞, 0
3. The ratio
of input impedance with feedback to without feedback is 1+Aβ
UNIT-6: Oscillators
SECTION-I
: Choose the correct answers
1.An
oscillator of LC type having a split capacitor in the tank circuit is [b ]
a. Hartley b. Colpitts c.
Tuned d. Wein Bridge
2. In a Crystal oscillator the frequency is very
stable due to ___________ of the crystal [c ]
a. rigidity b. high Q c.
vibration d. none
3. For generating a sinusoidal wave of 1KHz
frequency, the most suitable oscillator is ____ [ c]
(a) Hartley (b) Colpitts
(c) Wien bridge (d) None of the above
4. The frequency stability of LC oscillator is
_______ than RC oscillators. [
a]
(a) less (b) more (c)
either a or b (d) None of the above
5. An important limitation of a crystal
oscillator is ________. [ a]
(a) its low output (b) its
high Q (c) less availability of quartz crystal (d) its high output
SECTION-II: Fill in the blanks
1.
Non sinusoidal oscillators are also
called Multivibrators.
2.
The oscillator which uses inductive
feedback is Hartley
3.The
oscillator that uses tapped capacitors in the tuned circuit Armstrong
Oscillator.
4. Electronic oscillations in which amplitude
doesn’t change with time are called _
Sustained or Undamped oscillations
5 An oscillator
using LC tuned circuit has L= 58.6μH & C=300pF, then the frequency of
oscillations will be 1200
kHz
6. In a RC phase shift oscillator, each RC
section provides a phase shift of 60˚
UNIT-7: Large signal amplifiers
SECTION-I
: Choose the correct answers
1. With transformer connection to load the
maximum efficiency of the class A amplifier will go up to a maximum of [c ]
a. 78.5% b.25% c.50%
d.66%
2. The units of derating factor in power
amplifier is [b
]
a. Volts/oC b. Watts/ oC
c. Watts/ Cm2 d. None
3. In ____ power amplifier, the output
signal varies for a full 3600 of the cycle. [a ]
(a)Class A (b)
Class B (c) Class AB (d) None of the above
4. Maximum theoretical efficiency of
Class B push pull amplifier is ___. [d ]
(a)25.5% (b)
50% (c) 75% (d) 78.5%
SECTION-II: Fill in the blanks
1.
Thermal
resistance of the heat sink will be typically 30 C/W
2. If output power=20W and the input dc power=60W,then the
efficiency of power amplifier is 33.3%
3. In Class B power
amplifier, Q-point is set near cutoff
4. The input transformer in push-pull power amplifier is Step-up
5. The output transformer in push pull
power amplifier is Step down
UNIT-8:
Tuned amplifiers
SECTION-I
: Choose the correct answers
1. The
purpose of resonant circuits in tuned circuits is [d ]
a. TO provide properly
matching load impedence b. To reset unwanted harmonics
c. To couple power to load d. All of the above
2. To reduce further harmonic distortion in large signal tuned
amplifiers_______- is used [c
]
a. feedback
configuration b. transformer coupling
c. Push Pull configuration d. all of the can be used
3. In tuned amplifiers, harmonic distortion is ____________. [c ]
(a) Infinite (b) more (c) less (d) None
4. Double tuned amplifier provides ____ bandwidth than single tuned
amplifiers. [ a]
(a)larger (b) smaller (c) negligible (d)constant
5. Tuned
amplifiers can be used in _____. [c ]
(a)Radar (b) IF amplifiers (c) both a and b (d)
None
SECTION-II: Fill in
the blanks
1. Small signal tuned amplifiers are
operated in Class A mode.
2. Parallel tuned circuit is also known as Anti resonant circuit
Prepared
By
V.Neelima & Dhanalakshmi