# Analog Circuits Questions and Answers – Introduction to Oscillator

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

1. Oscillators are used to ______ AC voltage.
a) Prevent
b) Generate
c) Amplify
d) Rectify

Explanation: Oscillators are used for generating AC voltage. They are often characterized by the frequency of the oscillations produced. There are two main types of electronic oscillators, linear/harmonic and nonlinear/relaxation oscillator.

2. Oscillator __________ an AC input for giving an AC output.
a) Doesn’t need
b) Need
c) Doesn’t need at lower frequencies
d) Doesn’t need at higher frequencies

Explanation: An oscillator is an amplifier with positive feedback. It usually has a noise which is an amplifier as an oscillating output. They do not require any type of specific input to function properly.

3. Negative resistance are incorporated in oscillator for ___________
a) Sustained oscillation
b) Damped oscillation
c) Biasing the oscillator
d) Increasing amplitude of oscillation

Explanation: Negative resistance are incorporated in oscillator for sustained oscillation. Negative resistance will cancel the damping by positive (normal) resistance.

4. For accomplishing negative resistance in oscillator we use _____________
a) Voltage divider circuit
b) Negative feedback
c) Positive feedback
d) Current divider circuit

Explanation: The input or output impedance of an amplifier with positive feedback applied, can be negative. When loop gain is greater than 1, the input impedance is a negative value, over a linear range. These are also called active resistors.

5. Primary trigger for oscillation is obtained from ___________
a) DC voltage
b) Noise voltage
c) External trigger voltage
d) No trigger is required

Explanation: The primary trigger for oscillation is obtained from noise voltage.
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6. The AC power of output signal is obtained by ___________
a) Input AC voltage
b) Input DC voltage
c) DC biasing voltage
d) Power is generated by transistor itself

Explanation: The Ac power of output signal is obtained by DC biasing voltage of amplifier.

7. The output of a stable oscillator have ___________
a) Constant amplitude
b) Varying amplitude
c) Constant amplitude at high frequencies only
d) Constant amplitude at low frequencies only

Explanation: Output of a stable oscillator have constant amplitude and frequency. A common criteria is the Barkhausen stability criteria, wherein it states that loop gain should be unity and feedback should be positive.

8. The output waveform of a stable oscillator have ___________
a) Constant frequency at low amplitude only
b) Constant frequency at high amplitude only
c) Variable frequency
d) Constant frequency

Explanation: Output of a stable oscillator have constant amplitude and frequency.

9. In an oscillator if phase of feedback is same as that of oscillation waveform then feedback is called ___________
a) Positive feedback
b) Negative feedback
c) Cannot be predicted
d) Either positive or negative depending upon frequency

Explanation: In an oscillator if phase of feedback is same as that of oscillation waveform then feedback is called positive feedback.

10. The output of oscillator will not depend upon ___________
a) Feedback
b) Amplifier
c) Both feedback and amplifier
d) Input voltage

Explanation: The output of the oscillator will not depend upon input voltage. There is no input voltage for an oscillator.

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