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Electronics · 2nd Puc Science

Ch 6Oscillators — 2nd PUC Electronics, concept-first.

Almost every electronic system that generates, times or transmits a signal begins with a source of alternating voltage. A radio set, a television transmitter, a radar unit, a wristwatch and the clock inside a computer all rely on a circuit that produces a steady alternating (AC) waveform of a chosen frequency without a…

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Hartley Oscillator

The Hartley oscillator is an LC oscillator that uses inductive feedback from a centre-tapped inductor (L1, L2) with a capacitor C; it oscillates at f = 1/(2π√(LC)) with L = L1 + L2 and feedback factor β = L2/L1.

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Chapter contents

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Introduction

Almost every electronic system that generates, times or transmits a signal begins with a source of alternating voltage.

6.1

Introduction

An oscillator is an electronic circuit that converts DC energy into AC energy of a desired frequency. The AC sources it produces range from a few hertz to several gigahertz, which is why oscillators s…

6.2

Oscillatory circuit or tank circuit

A circuit that produces electrical oscillations of any desired frequency is called an oscillatory circuit or tank circuit.

6.3

RC Oscillators

RC oscillators use resistors and capacitors, instead of inductors, to generate low-frequency signals. The two important RC oscillators in the II PUC Electronics syllabus are the phase-shift oscillator…

6.4

Crystal oscillator

A crystal oscillator replaces the LC or RC tank with a vibrating quartz crystal, giving far higher frequency stability.

6.5

Non sinusoidal Oscillator

So far every oscillator produced a sine wave. A non-sinusoidal oscillator produces a repeating output of some other shape, and the standard device for building one is the 555 timer.

Chapter Summary

- An oscillator converts DC energy into AC energy of a desired frequency (a few Hz to several GHz) with no AC input, using an amplifier with positive feedback.

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+Show 13 questions13 questions
  1. Example 1A Hartley Oscillator has \(L_1 = 2\,\text{mH}\), \(L_2 = 4\,\text{mH}\) and \(C = 10\,\text{nF}\). Determine the frequency of oscillation.Free
  2. Example 2A Hartley oscillator circuit is to generate a frequency of \(24\,\text{kHz}\). The inductors used have inductances \(L_1 = 1\,\text{mH}\) an…Free
  3. Example 3The frequency of Hartley oscillator is \(20\,\text{kHz}\). The capacitor used in the feedback network has a value of \(576\,\text{pF}\). If…Free
  4. Example 4Calculate the frequency and feedback factor of the circuit shown below. ![Hartley feedback tank network. Two terminals on the left, both lab…Preview
  5. Example 5A transistor Colpitts oscillator has \(L = 10\,\text{mH}\), \(C_1 = 0.1\,\mu\text{F}\) and \(C_2 = 0.1\,\mu\text{F}\). Determine the frequen…Preview
  6. Example 6The frequency of Colpitts oscillator is \(18\,\text{MHz}\). Design the value of inductor to be used if \(C_1 = 100\,\text{pF}\) and \(C_2 =…Preview
  7. Example 7Calculate the frequency and feedback factor of the circuit shown below. ![Colpitts feedback tank network. Two terminals on the left, both la…Preview
  8. Example 8A RC phase shift oscillator has \(R_1 = R_2 = R_3 = R = 10\,k\Omega\) and \(C_1 = C_2 = C_3 = C = 0.047\,\mu\text{F}\). Determine the freque…Preview
  9. Example 9What should be the capacitance value of the capacitor required for a phase shift oscillator of frequency \(120\,\text{Hz}\), if the resistor…Preview
  10. Example 10The frequency of the phase shift oscillator is \(78\,\text{Hz}\). If the value of capacitance of the capacitor used is \(220\,\text{nF}\). C…Preview
  11. Example 11A Wein bridge Oscillator has \(R_1 = R_2 = R = 15\,k\Omega\) and \(C_1 = C_2 = 100\,\text{nF}\). Determine the frequency of oscillation.Preview
  12. Example 12The frequency of the Wein bridge oscillator is \(75\,\text{Hz}\). If the capacitance value used is \(0.22\,\mu\text{F}\), calculate the valu…Preview
  13. Example 13The frequency of the Wein bridge oscillator is \(100\,\text{Hz}\). If the resistance value used is \(12\,k\Omega\). Calculate the value of c…Preview
+Show 14 questions14 questions
  1. Q1A transistor Colpitts oscillator has \(L = 4\,\text{mH}\), \(C_1 = 10\,\text{nF}\) and \(C_2 = 10\,\text{nF}\). Determine the frequency of o…Free
  2. Q2A Colpitts oscillator circuit is to generate a frequency of \(24\,\text{kHz}\). The capacitors used are \(C_1 = 0.2\,\mu\text{F}\) and \(C_2…Free
  3. Q3A Colpitts oscillator oscillates at \(1.13\,\text{MHz}\). If the inductor in the feedback network has a value of \(20\,\mu\text{H}\) and one…Free
  4. Q4Calculate the frequency and feedback ratio of the circuit shown below. ![Colpitts feedback tank network (uncaptioned). Two terminals on the…Preview
  5. Q5A Hartley oscillator has \(L_1 = 3\,\text{mH}\), \(L_2 = 5\,\text{mH}\) and \(C = 10\,\text{nF}\). Determine the frequency of oscillations.Preview
  6. Q6A Hartley oscillator circuit is to generate a frequency of \(1200\,\text{kHz}\). If the capacitor in the feedback network has a value of \(2…Preview
  7. Q7A Hartley oscillator oscillates at \(54\,\text{kHz}\). The inductors used have inductances \(L_1 = 30\,\text{mH}\) and \(L_2 = 60\,\text{mH}…Preview
  8. Q8Calculate the frequency and feedback ratio of the circuit shown below. ![Hartley feedback tank network (uncaptioned). Two terminals on the l…Preview
  9. Q9A RC phase shift oscillator uses three identical RC sections in the feedback network. The values of the components are \(R = 680\,\Omega\) a…Preview
  10. Q10What should be the value of capacitor required for a phase shift oscillator to produce a frequency of \(338\,\text{Hz}\), if the resistance…Preview
  11. Q11The frequency of the phase shift oscillator is \(125\,\text{Hz}\). If the value of capacitance of the capacitor used is \(0.22\,\mu\text{F}\…Preview
  12. Q12The frequency of the Wein bridge oscillator is \(1200\,\text{Hz}\). If the resistance value used is \(820\,\Omega\), calculate the value of…Preview
  13. Q13The RC network of Wein bridge oscillator consists of resistors and capacitors of values \(R_1 = R_2 = R = 270\,k\Omega\) and \(C_1 = C_2 = C…Preview
  14. Q14The frequency of the Wein bridge oscillator is \(1500\,\text{Hz}\). If the capacitance value used is \(C_1 = C_2 = C = 0.1\,\mu\text{F}\), c…Preview
+Show 29 questions29 questions
  1. Q1What is positive feedback?Free
  2. Q2What is an oscillator?Free
  3. Q3What are sinusoidal oscillators?Free
  4. Q4What are non-sinusoidal or relaxation oscillators?Preview
  5. Q5What are damped oscillations?Preview
  6. Q6What are undamped oscillations?Preview
  7. Q7Write the expression for voltage gain of a positive feedback.Preview
  8. Q8Draw the basic block diagram of an oscillator.Preview
  9. Q9What is a tank circuit?Preview
  10. Q10What should be the value of loop gain to start oscillations?Preview
  11. Q11What should be the value of loop gain for sustained oscillations?Preview
  12. Q12How many RC branches are required for a phase shift oscillator?Preview
  13. Q13What is the amount of phase shift in each RC section of a phase shift oscillator?Preview
  14. Q14Write the expression for frequency of oscillations of a Wein bridge oscillator.Preview
  15. Q15Write the expression for frequency of oscillations of a RC phase shift oscillator.Preview
  16. Q16Write the expression for frequency of oscillations of a Colpitts oscillator.Preview
  17. Q17Write the expression for frequency of oscillations of a Hartley oscillator.Preview
  18. Q18Write the expression for frequency of oscillations of a crystal oscillator.Preview
  19. Q19Does the bridge circuit produce any phase shift in the Wein bridge oscillator?Preview
  20. Q20Write the expression for the feedback factor of a Colpitts oscillator.Preview
  21. Q21Write the expression for the feedback factor of a Hartley oscillator.Preview
  22. Q22Write the expression for the feedback factor of a phase shift oscillator.Preview
  23. Q23Write the expression for the feedback factor of Wein bridge oscillator.Preview
  24. Q24Mention the principle used in crystal oscillator.Preview
  25. Q25What is the type of feedback used in Colpitts oscillator?Preview
  26. Q26What is the type of feedback used in Hartley oscillator?Preview
  27. Q27Draw the symbol of crystal.Preview
  28. Q28Draw the electrical equivalent circuit of crystal.Preview
  29. Q29Draw the pin diagram of 555 timer.Preview
+Show 16 questions16 questions
  1. Q1Distinguish between sinusoidal and relaxation oscillators.Free
  2. Q2Distinguish between damped and un damped oscillationsFree
  3. Q3Explain briefly the conditions of Barkhausen criterion.Free
  4. Q4Draw the circuit diagram of a Hartley oscillator.Preview
  5. Q5Draw the circuit diagram of a Colpitts oscillator.Preview
  6. Q6Draw the circuit diagram of a RC phase shift oscillator.Preview
  7. Q7Draw the circuit diagram of a Wein bridge oscillator.Preview
  8. Q8Draw the circuit diagram of a crystal oscillator.Preview
  9. Q9Write any two applications of a Hartley oscillator.Preview
  10. Q10Mention any two applications of a Colpitts oscillator.Preview
  11. Q11Mention any two advantages of a crystal oscillator over LC and RC oscillators.Preview
  12. Q12Mention the limitations of LC and RC oscillators.Preview
  13. Q13Write any two advantages of RC oscillators over LC oscillators.Preview
  14. Q14Mention any two applications of a crystal oscillator.Preview
  15. Q15Draw the block diagram of 555 timer.Preview
  16. Q16Draw the block diagram of a bistable multivibrator.Preview
+Show 8 questions8 questions
  1. Q1Explain briefly how the oscillations are produced in a tank circuit.Free
  2. Q2With a circuit diagram, explain the principle of phase shift in RC circuit.Free
  3. Q3With a circuit diagram, explain the principle of lead lag network.Free
  4. Q4Draw the circuit diagram of a Hartley oscillator. Mention the expression for its frequency of oscillations.Preview
  5. Q5Draw the circuit diagram of a Colpitts oscillator. Mention the expression for its feedback factor.Preview
  6. Q6Draw the circuit diagram of a RC phase shift oscillator. Draw its output wave form.Preview
  7. Q7Draw the circuit diagram of a Wein bridge oscillator. Mention the expression for its voltage gain.Preview
  8. Q8Draw the circuit diagram of crystal oscillator. Draw the electrical equivalent circuit of a crystal.Preview
+Show 6 questions6 questions
  1. Q1With a circuit diagram, explain the working of a Hartley oscillator. Write the expression for its frequency and feedback factor.Free
  2. Q2Draw the circuit diagram of Colpitts oscillator and explain its action. Write the expression for its frequency and feedback factor.Free
  3. Q3With a circuit diagram explain the action of a RC phase shift oscillator. Write the expression for its frequency and feedback factor.Preview
  4. Q4Draw the circuit diagram of a Wein bridge oscillator and explain its working. Write the expression for its frequency and feedback factor.Preview
  5. Q5With a circuit diagram, explain the working of crystal oscillator. Write the expression for its frequency of oscillation.Preview
  6. Q6Explain briefly each part of block diagram of 555timer.Preview