# Analog Circuits Questions and Answers – Hartley Oscillator-2

This set of Analog Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Hartley Oscillator-2”.

1. If L1 and L2 are the inductance used in the Hartley oscillator, the effective inductance in the equation of frequency calculation is equal to (Without considering mutual inductance).
a) (L1×L2)/(L1+L2)
b) L22/(L1+L2)
c) L1+L2
d) L1-L2

Explanation: Inductance L1 and L2 are series and hence effective inductance without mutual inductance will be L1+L2.

2. Which configuration of the transistor amplifier is used for Hartley oscillator?
a) Common emitter amplifier
b) Common collector amplifier
c) Common base amplifier
d) Combination of both common emitter and common collector

Explanation: Common emitter transistor configuration is used in Hartley oscillator to ensure good oscillation.

3. Phase shift provided by the overall tank circuit in Hartley oscillator is __________
a) 0 degree
b) 90 degree
c) 180 degree
d) -90 degree

Explanation: Phase shift provided by the tank circuit is 180 degrees to obey Barkhausen’s criteria for sustained oscillation.

4. The gain device in the Hartley oscillator act as a __________
a) Low pass filter
b) High pass filter
c) Band pass filter
d) Band rejection filter

Explanation: The gain device in Hartley oscillator act as a band pass filter.

5. The phase difference produced by the active element of Hartley oscillator is __________
a) 0 degree
b) 180 degree
c) 90 degree
d) 120 degree

Explanation: The coil has a tap such that the proper phase is available to the base of the transistor. Value of L and C are adjusted to give a phase shift of 180°. The transistor itself creates a 180° phase shift and hence total shift is 360°/0.
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6. Hartley oscillator make use of ________ amplifiers.
a) Class A
b) Class B
c) Class C
d) Class D

Explanation: Hartley oscillator make use of class C amplifiers because it can amplify signals less than 180 degrees and provide output of full cycle.

7. The Hartley oscillator is less preferred than due to Colpitts oscillator’s performance in __________
a) All frequency region
b) Mid frequency region
c) High frequency region
d) Low frequency region

Explanation: The Hartley oscillator is less preferred than due to Colpitts oscillator’s performance in high frequency regions due to stability. Colpitt’s oscillator uses a capacitive voltage divider setup which provides better stability than an inductive voltage divider as in Hartley oscillator.

8. Example for a self-limiting oscillator is __________
a) Hartley oscillator
b) Weinbridge Oscillator
c) RC phase shift oscillator
d) Astable multivibrator

Explanation: LC oscillators are also called self-limiting oscillators.

9. What will be the oscillator frequency of Hartley oscillator if inductance L1, L2 are equal to 1mH and 2mH respectively and capacitor C is 10nF. (Neglect mutual inductance)
a) 50KHz
b) 29KHz
c) 40KHz
d) 57 kHz

Explanation: L1 = 1mH
L2 = 2mH
Effective inductance L = L1+L2 = 1+2 = 3mH
C = 10nF
Oscillator frequency .
Frequency = 29kHz.

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