Oscillators – Exercise – 1

1. For generating 1 kHz signal, the most suitable circuit is :

(a)  colpitts oscillator
(b)  hartley oscillator
(c)  tuned collector oscillator
(d)  wien bridge oscillator

Answer
Answer : (d)
Explanation
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2. The feedback factor β at the frequency of oscillation of a Wien bridge oscillator is :

(a)  3
(b)  1/3
(c)  1/29
(d)  3/29

Answer
Answer : (b)
Explanation
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3. The use of crystal in a tunable oscillator :

(a)  improves frequency stability
(b)  increases the gain of the oscillator
(c)  helps to obtain optimum output impedance
(d)  facilitates generation of wide range of frequencies

Answer
Answer : (a)
Explanation
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4. A phase shift oscillator uses :

(a)  LC tuning
(b)  piezoelectric crystal
(c)  balanced bridge
(d)  variable frequency operation

Answer
Answer : (c)
Explanation
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5. A highly stable resonance characteristic is the property of a …….. oscillator.

(a)  hartley
(b)  colpitts
(c)  crystal
(d)  wein bridge

Answer
Answer : (c)
Explanation
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6. The main advantage of a crystal oscillator is that its output is :

(a)  50Hz to 60Hz
(b)  variable frequency
(c)  a constant frequency
(d)  direct current

Answer
Answer : (c)
Explanation
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7. An oscillator of the LC type that has a split capacitor in the circuit is :

(a)  hartley oscillator
(b)  colpitts oscillator
(c)  wein bridge oscillator
(d)  R-C phase shift oscillator

Answer
Answer : (b)
Explanation
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8. Wein bridge oscillator can typically generate frequencies in the range of :

(a)  1KHz – 1MHz
(b)  1 MHz – 10MHz
(c)  10MHz – 100MHz
(d)  100MHz – 150MHz

Answer
Answer : (a)
Explanation
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9. The frequency of oscillation of a tunnel-collector oscillator having L= 30 µH and C = 300 pf is nearby :

(a)  267 kHz
(b)  1677 kHz
(c)  1.68 kHz
(d)  2.67 MHz

Answer
Answer : (b)
Explanation
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10. Which of the following is the most stable oscillator ?

(a)  Wein bridge oscillator
(b)  Hearley-oscillator
(c)  Colpilts oscillator
(d)  Crystal controlled oscillator

Answer
Answer : (d)
Explanation
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11. Barkhausen criterion for oscillator stability is :

(a)  Aβ = 0
(b)  Aβ = 1
(c)  –Aβ = 1
(d)  A = 1/√β

Answer
Answer : (c)
Explanation
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12. A Hartley oscillator circuit uses :

(a)  Capacitive feedback
(b)  A tapped inductor
(c)  A tapped capacitor
(d)  A tapped inductor for inductive feedback

Answer
Answer : (d)
Explanation
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13. For good stability, the tuned circuit should have :

(a)  High Q
(b)  Low R
(c)  Low L
(d)  Low C

Answer
Answer : (a)
Explanation
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14. The varactor in a voltage controlled oscillator needs :

(a)  Audio signal below 1000 Hz
(b)  Reverse D.C control voltage
(c)  Forward bias
(d)  Parallel capacitance were than 5μF

Answer
Answer : (b)
Explanation
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15. In a practical oscillator is :

(a)  Slightly less than 1
(b)  1
(c)  -1
(d)  Slightly greater than 1

Answer
Answer : (d)
Explanation
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16. Oscillators have :

(a)  No feedback
(b)  Negative feedback
(c)  Positive feedback
(d)  Either positive or negative feedback

Answer
Answer : (c)
Explanation
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(a) (b) (c) (d) Answer : () [/su_spoiler]
Explanation
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18. For oscillator to start, the loop gain of the oscillator must be :

(a)  Infinitely high
(b)  More than one
(c)  Exactly one
(d)  Less than one

Answer
Answer : (b)
Explanation
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19. Which of the following is an oscillator with best frequency stability ?

(a)  Crystal oscillator
(b)  Clapp oscillator
(c)  Phase shift circuit
(d)  Multi vibrator

Answer
Answer : (a)
Explanation
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