Clapp Oscillator - Analog Circuits Questions and Answers

This set of Analog Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Clapp Oscillator”.

1. Clapp oscillator is an ___________
a) LC oscillator
b) RC oscillator
c) RL oscillator
d) Crystal oscillator
View Answer

Answer: a
Explanation: Clapp oscillator is a colpitts oscillator which has an extra capacitor series with an inductor. Hence it is an LC oscillator, with 3 capacitors and one single inductor to set its frequency, and the clap circuit is often used as a variable frequency oscillator, by making one capacitor variable.

2. Which type of feedback is used in clapp oscillator?
a) Positive feedback
b) Negative feedback
c) No feedback is used
d) Both positive and negative feedback
View Answer

Answer: a
Explanation: Positive feedback is present in the clap oscillator, where in the three capacitors form a voltage divider which determines amount of feedback being applied to transistor input.

3. When constructing variable frequency oscillator among clapp oscillator and colpitts oscillator which one is preferred?
a) Colpitts oscillator
b) Clapp oscillator
c) Both of them have equal preference
d) None of them preffered
View Answer

Answer: b
Explanation: The stray third capacitor in the clap oscillator doesn’t have a negative effect and the frequency obtained is instead more stable and accurate than colpitt oscillator, hence the clap oscillator is preferred for a variable frequency oscillator.

4. In clapp oscillator voltage is divided by using __________
a) Resistors
b) Capacitors
c) Inductors
d) Voltage dividing circuits are not used
View Answer

Answer: b
Explanation: In clap capacitor voltage divider circuit is achieved by capacitor because it is a modified version of colpitts oscillator.

5. In a clapp oscillator with three capacitor C₁, C₂, C₃, C₁ is used as upper capacitor in voltage divider, C₂ is used as lower capacitor in voltage divider and C₃ is the third capacitor. For perfect operation which of these capacitor should have minimum value?
a) C₁
b) C₂
c) C₃
d) All of them are equal
View Answer

Answer: c
Explanation: In a Clapp oscillator C₃ is much smaller than C₁ and C 2as a result, the equivalent capacitance C is approximately equal to C₃. For perfect operation C₃ should have minimum value.

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6. In a clapp oscillator with three capacitor C₁, C₂, C₃, C₁ is used as upper capacitor in voltage divider, C₂ is used as lower capacitor in voltage divider and C₃ is the third capacitor. The frequency of operation will be close to (Assume C₁ parallel C₂ is C₃).
a)
b)
c)
d)
View Answer

Answer: c
Explanation: Since equivalent capacitance is close to C₃ and equation is similar to colpitts oscillator.

7. In a clapp oscillator with three capacitor C₁, C₂, C₃, C₁ is used as upper capacitor in voltage divider, C₂ is used as lower capacitor in voltage divider and C₃ is the third capacitor. For perfect operation of clapp oscillator value of C₃ should be __________
a) Equal to C₁
b) Equal to C₂
c) Equal to C₁ parallel C₂
d) Very small
View Answer

Answer: c
Explanation: For perfect operation of clapp oscillator value of C₃ should be C₁ parallel C₂.

8. In a clapp oscillator with three capacitor C₁, C₂, C₃, C₁ is used as upper capacitor in voltage divider, C₂ is used as lower capacitor in voltage divider and C₃ is the third capacitor. Inductance used in the circuit is L. The frequency of operation will be __________
a)
b)
c)
d)
View Answer

Answer: a
Explanation: The frequency of operation is given

. Here effective capacitance is equal to C parallel C₂ parallel C₃.

9. In the following oscillator which one is more accurate?
a) Colpitts oscillator
b) Clapp oscillator
c) Hartley oscillator
d) Simple LC oscillator
View Answer

Answer: b
Explanation: The stray third capacitor in the clap oscillator doesn’t have a negative effect and the frequency obtained is instead more stable and accurate than colpitt oscillator.

10. What will be the clapp oscillator frequency if the C₁, C₂, C₃ of clap oscillator is 1μF, 1μF, 2μF respectively and inductance is 1μH?
a) 0.1MHz
b) 0.4MHz
c) 1MHz
d) 4MHz
View Answer

Answer: b
Explanation: Frequency of clap oscillator is

= 3.9 x 10⁵ ie approximately 0.4MHz.
Therefore, frequency is equal to