Colpitt oscillator

1,870 views

Published on

colpitt oscillator its advantages and its applications

Published in: Engineering, Technology, Business
0 Comments
6 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
1,870
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
112
Comments
0
Likes
6
Embeds 0
No embeds

No notes for slide

Colpitt oscillator

  1. 1. BY HARSHA VARDHAN.K COLPITT OSCILLATOR
  2. 2. Oscillator: An oscillator is a circuit that produces a repetitive signal from a dc voltage. The Colpitts oscillator is known for using a capacitor voltage divider as its feedback source
  3. 3. Circuit diagram:
  4. 4.  The Colpitts oscillator is a type of oscillator that uses an LC circuit in the feed-back loop.  The feedback network is made up of a pair of tapped capacitors (C1 and C2) and an inductor L to produce a feedback necessary for oscillations
  5. 5.  The output voltage is developed across C1.  The feedback voltage is developed across C2
  6. 6. Frequency of oscillations
  7. 7. Conditions for Oscillation and Startup  Values of C1 and C2 determine the attenuation as or But for Oscillation
  8. 8. For the oscillator to be self starting,  Loading Effect on FeedbackCircuit  Input impedance of the amplifier acts as a load on the resonant feedback circuit and reduces the quality factor of the circuit When Q>10 When Q<10, the resonant frequency is significantly reduced
  9. 9.  To avoid this loading effect, we can use JFET instead of BJT as it has very high input impedance as compared to BJT.
  10. 10. Frequency Stability  Use high stability capacitors, e.g. silver mica, polystyrene, or teflon capacitors and low temperature coefficient inductors for high stable oscillators.
  11. 11. Amplitude Stability  In order to start the oscillation, the loop gain is usually slightly greater than unity.  LC oscillators in general do not require amplitude stabilization circuits because of the selectivity of the LC circuits.  In RC oscillators, some non-linear devices, e.g. NTC/PTC resistors, FET or zener diodes can be used to stabilized the amplitude
  12. 12. Advantages:  Good wave purity  Fine performer at high frequency  Good stability at high frequency  Wide operation range 1 to 60 MHz Disadvantages:  Poor isolation (Load impedance v.s. frequency)  Hard to design
  13. 13. Applications:  to generate the sinusodal waveform(to generate sustained oscillations)  Oscillator design and simulation is a complicated process. It is also extremely important and crucial to design a good and stable oscillator
  14. 14.  Oscillators are commonly used in communication circuits. All the communication circuits for different modulation techniques—AM, FM, PM—the use of an oscillator is must.  Oscillators are used as stable frequency sources in a variety of electronic applications.  Oscillator circuits are used in computer peripherals, counters, timers, calculators, phase-locked loops, digital multi-metres, oscilloscopes, and numerous other applications

×