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Negative Feedback Amplifiers<br />                  Guided by : Prof. S. S. Patil<br />       Presentation by: Vinay  Jasu...
TOPICS TO BE COVERED<br />Introduction<br />Concept of Feedback<br />Feedback Topologies<br />General Characteristics of N...
Introduction<br />Feedback (Definition)<br />                   It is the process in which part of the output signal is re...
Difference Between Positive &Negative Feedback<br />
CONCEPT OF FEEDBACK<br />
Amplifiers Without Feedback<br />Amplifier<br />“A”<br />Vi<br />Vo<br />
Amplifiers With Feedback<br />Sampling Network<br />Amplifier<br />“A”<br />Mixer<br />Vo<br />Vs<br />Vi<br />Vo<br />Fee...
Transfer characteristics with feedback (Af )<br />Stabilization of Gain<br />Effect on input resistance<br />Effect on out...
Transfer characteristics with feedback (Af )<br />A = Transfer gain without feedback<br />A  = Transfer gain with feedback...
Stabilization of Gain<br />Fractional Change in amplification with feedback is given by<br /> Factors affecting  stability...
Sensitivity and Desensitivity<br />
Effect on input resistance and output resistance<br />
Analysis Of Feedback Amplifiers<br />Step 1: Identify the topology.<br />Step 2: Draw the basic amplifier circuit without ...
Voltage Series Feedback<br />Make V0=0 If  Vf=0 then voltage sampling.<br />Feedback voltage Vf  is in series with the inp...
Approximate h-parameter equivalent circuit<br />
Current Series Feedback<br />Set output current Io=0 if Vf=0 then current sampling.<br />Feedback voltage Vf  is in series...
h-parameter equivalent circuit<br />
-Re <br />
Current Shunt Feedback<br /><ul><li>Set output current Io=0 if Vf=0 then current sampling.
Feedback signal is in parallel . Hence it is current shunt feedback. </li></ul>Current shunt feedback<br />
h-parameter equivalent circuit<br />
Voltage Shunt Feedback<br /><ul><li>Make V0=0 If  Vf=0 then voltage sampling.
Is= Ii +If   .It is series mixing.
Feedback is voltage shunt feedback.</li></ul>Voltage shunt feedback<br />
h-parameter equivalent circuit<br />
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Transcript of "Final"

  1. 1. Negative Feedback Amplifiers<br /> Guided by : Prof. S. S. Patil<br /> Presentation by: Vinay Jasud (52)<br /> Vinod Arote (54)<br />
  2. 2. TOPICS TO BE COVERED<br />Introduction<br />Concept of Feedback<br />Feedback Topologies<br />General Characteristics of Negative Feedback Amplifiers<br />Analysis Of Feedback Amplifiers<br />Voltage Series Feedback<br />Voltage Shunt Feedback<br />Current Series Feedback<br />Current Shunt Feedback<br />
  3. 3. Introduction<br />Feedback (Definition)<br /> It is the process in which part of the output signal is returned back to the input.<br />Types of Feedback<br /> 1.Positive Feedback<br /> 2. Negative Feedback<br />
  4. 4. Difference Between Positive &Negative Feedback<br />
  5. 5. CONCEPT OF FEEDBACK<br />
  6. 6. Amplifiers Without Feedback<br />Amplifier<br />“A”<br />Vi<br />Vo<br />
  7. 7. Amplifiers With Feedback<br />Sampling Network<br />Amplifier<br />“A”<br />Mixer<br />Vo<br />Vs<br />Vi<br />Vo<br />Feedback<br />Signal<br />Vf<br />Feedback Network<br />Feedback factor<br />
  8. 8. Transfer characteristics with feedback (Af )<br />Stabilization of Gain<br />Effect on input resistance<br />Effect on output resistance<br />Effect on Bandwidth<br />Effect on nonlinear distortion<br />Effect on noise<br />General Characteristics Of Negative Feedback Amplifiers<br />
  9. 9. Transfer characteristics with feedback (Af )<br />A = Transfer gain without feedback<br />A = Transfer gain with feedback<br />f<br />f<br /> o<br />Where X = Feedback Signal<br />X = output signal<br />f<br />o<br />Transfer gain with feedback is given by<br />
  10. 10. Stabilization of Gain<br />Fractional Change in amplification with feedback is given by<br /> Factors affecting stability are aging, temperature changes, replacement of component. <br />f<br />f<br />
  11. 11. Sensitivity and Desensitivity<br />
  12. 12. Effect on input resistance and output resistance<br />
  13. 13. Analysis Of Feedback Amplifiers<br />Step 1: Identify the topology.<br />Step 2: Draw the basic amplifier circuit without feedback.<br />Step 3: Use Thevenin’s theorem for voltage source and Norton’s theorem for current sou.rce.<br />Step 4: Replace each device by it’s h-parameter.<br />Step 5: Indicate Xo and Xf and evaluate .<br />Step 6: Calculate open loop gain A.<br />Step 7: Calculate D, Af, Rif and Rof.<br />
  14. 14. Voltage Series Feedback<br />Make V0=0 If Vf=0 then voltage sampling.<br />Feedback voltage Vf is in series with the input voltage Vs .Therefore series mixing.<br /> voltage sampling + series mixing =Voltage series feedback<br />Transistor emitter follower circuit<br />
  15. 15. Approximate h-parameter equivalent circuit<br />
  16. 16.
  17. 17. Current Series Feedback<br />Set output current Io=0 if Vf=0 then current sampling.<br />Feedback voltage Vf is in series with the input voltage Vs .Therefore series mixing.<br />Therefore current series feedback. <br />CE transistor amplifier with unbypassed Re<br />
  18. 18. h-parameter equivalent circuit<br />
  19. 19. -Re <br />
  20. 20. Current Shunt Feedback<br /><ul><li>Set output current Io=0 if Vf=0 then current sampling.
  21. 21. Feedback signal is in parallel . Hence it is current shunt feedback. </li></ul>Current shunt feedback<br />
  22. 22. h-parameter equivalent circuit<br />
  23. 23.
  24. 24. Voltage Shunt Feedback<br /><ul><li>Make V0=0 If Vf=0 then voltage sampling.
  25. 25. Is= Ii +If .It is series mixing.
  26. 26. Feedback is voltage shunt feedback.</li></ul>Voltage shunt feedback<br />
  27. 27. h-parameter equivalent circuit<br />
  28. 28.
  29. 29. Questions ???<br />
  30. 30. Thank You<br />
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