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COLLEGE OF ENGINEERING & TECHNOLOGY
Department
Lecturer
T. Assistant
Course
Course Code
: Electronics & Communications Engineering
: Dr. Iman Morsi
: Eng. Salma Darwish
: Electronic Measurements
: EC410
Sheet (3)
LC – RLC Oscillators
1. Describe the two basic radio frequency Oscillators.
2. Explain the working of Hartley oscillation and how does it satisfy the basic
condition for oscillations?
3. Why is Hartley oscillation not suitable for low frequency work?
4. What are the conditions of oscillation in the Hartley and Colpitts
Oscillators?
5. In order to sustain oscillation in a Hartley oscillator, what will be the
minimum value of the feedback resistor and frequency of oscillation with
Ri=15 kΩ, L1 = 10 μH, L2 = 270 μH, and C = 0.001μf?
6. A Hartley oscillator has Ri= 10 kΩ, C = 0.015 μf, L1 = 15 μH. Determine the
value of L2 if the frequency of oscillation is to be 100 kHz.
7. Determine the operating frequency of a Colpitts’s oscillator with circuits
values L=100 µH, C1=0.005 µF and C2=0.01 µF.
8. What will be the ratio of the highest to the lowest frequency of an
oscillator if a 50 to 350 pF variable capacitor is used in the tuned circuit?
9. An amplifier with feedback has voltage gain of 40. To produce a specified
output, the input voltage required without feedback is 0.1v. When feedback
has been provided the input must be increased to 2.4v to produce the same
output. Calculate the value of feedback ratio.
10. The ac equivalent circuit of the crystal has a resistance of 2000Ω, L=1.2H
and C1=0.02pF, C2=0.01pF. Determine the two resonant frequencies.
11. Compare between the Wein Bridge, Phase Shift Oscillator, Hartley, Colpitt
and Crystal Oscillators from the point of view of:a. The Circuit diagram.
b. The Advantages and Disadvantages.
c. The applications.
d. The Fr equation.