MCQs on Analog Electronics

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01․ The feedback factor of a Wien bridge oscillator using Op-Amp is

At the resonant frequency, the feedback factor (R2/R1) of a Wien bridge oscillator using Op-Amp, is 1/2. Hence, the amplifier gain must be greater than 2 to maintain sustained oscillations.

02․ For audio frequency applications, the popular oscillator used is
Wien bridge oscillator
Hartley oscillator
Crystal oscillator
Phase shift oscillator

Characteristics like ease of tuning, very low distortion and good frequency stability of Wien bridge oscillator makes it becomes popular for audio frequency applications. Phase shift oscillator and Wien bridge oscillator both can be used as audio frequency range. But Wien bridge oscillator can be used for very wide frequency range.

03․ Colpitts oscillator is also called as
Tank circuit oscillator
LC oscillator
Resonant circuit oscillator
All of the above

Colpitts oscillator is one of the type of LC oscillator which consisting of resonant tank circuit. The tank circuit consists of two series capacitor parallel with a inductor. Therefore, we can call any of the names mentioned above.

04․ A quartz crystal oscillator consists of
only series resonant frequency.
only parallel resonant frequency.
both series and parallel frequencies.
neither series nor parallel frequency.

Crystal Oscillator has two closely spaced resonant frequency. In crystal oscillator, series resonant frequency occurs when reactance of the capacitor is equal to the reactance of the inductor (low impedance). Parallel resonant frequency occurs when reactance of the capacitor C2 is equal to the reactance of RLC1 branch (High impedance).

05․ Which oscillators are easy to fabricate in a monolithic IC?
Crystal oscillator.
Hartley oscillator.
Wien bridge oscillator.
Relaxation oscillator.

Relaxation oscillators do not use inductor and its output depends on nonlinear characteristics of the circuit. Therefore, a relaxation can be easily fabricated in a monolithic IC's.

06․ Which of the following is not a sinusoidal oscillator?
LC oscillator
RC phase shift oscillator
Relaxation oscillator
Crystal oscillator

Relaxation oscillator is basically a non-sinusoidal oscillator which is used to generate square, triangular or pulse waveforms. The rest of the oscillators are sinusoidal oscillators producing sinusoidal output.

07․ Voltage controlled oscillators are used commonly in
Pulse Modulators Frequency Modulators Phase Clocked loops
Frequency Modulators
Phase Clocked loops
All the above

VCOs are commonly used in electronic jamming equipment, function generator, for production of different types of noise, phase locked loop, frequency synthesizers or modulators used in communication circuits etc.

08․ One of the following is the primary function of an oscillator
produces sinusoidal oscillations
generates non sinusoidal waveforms
generates sustained oscillations at a constant amplitude and specific frequency
none of the above

The oscillating nature of a circuit make it as oscillator. But to produce sustained oscillations in a controllable and desired manner and has to satisfy Bark-hausen criterion.

09․ Relaxation Voltage controlled oscillators are used to generate
Sinusoidal wave
Triangular wave
Sawtooth wave
Both B and C

Relaxation VCOs can be employed to generate both triangular and saw-tooth waveforms.

10․ Feedback circuit in an oscillator can be accomplished by
Resistive coupling between input and output
Capacitive coupling between input and output
Inductive coupling between input and output
Any one or combinations of the above methods

For different type of applications, oscillators can be built with different feedback circuit to produce proper phase and amplitude. These types of oscillators include RC and LC oscillators. Colpitts oscillators uses capacitive feedback, Hartley oscillator uses inductive feedback.