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Thought of the Day

Thought of the Day. When you meet other people, look them in the eye, state your name clearly, and shake hands firmly. Small-Signal Amplifier. D.C. Kulshreshtha. 2. Equivalent Circuit Method. The transistor is replaced by its ac equivalent circuit model.

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Thought of the Day

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  1. Thought of the Day When you meet other people, look them in the eye, state your name clearly, and shake hands firmly. Electronic Amplifiers

  2. Small-Signal Amplifier D.C. Kulshreshtha Electronic Amplifiers

  3. 2. Equivalent Circuit Method • The transistor is replaced by its ac equivalent circuit model. • Modelling of FET is much simpler than that of BJT, because of two reasons : • BJT is current operated devices • The output affects the input. • For BJT, we have either h-parameter model or hybrid-π model. Electronic Amplifiers

  4. Hybrid Parameters Electronic Amplifiers

  5. Electronic Amplifiers

  6. Electronic Amplifiers

  7. Electronic Amplifiers

  8. Complete h-parameter circuit model of a BJT. Electronic Amplifiers

  9. Simplified h-parameter model of a BJT. Electronic Amplifiers

  10. Hybrid-πCircuit Model Electronic Amplifiers

  11. Vce = 0 means output shorted. Whole current flows through the short. Electronic Amplifiers

  12. From the input of the circuit : Electronic Amplifiers

  13. Equivalent circuit method of AC Analysis Electronic Amplifiers

  14. Electronic Amplifiers

  15. Electronic Amplifiers

  16. Input Resistance Electronic Amplifiers

  17. Output resistance Electronic Amplifiers

  18. How Small is Small Peak-to-peak current should be less than 10 % of dc current. Electronic Amplifiers

  19. Example : Analyze the CE amplifier circuit using h-parameter model of BJT. Electronic Amplifiers

  20. Electronic Amplifiers

  21. Electronic Amplifiers

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  23. Electronic Amplifiers

  24. Note: Since 1/hoe can be ignored, the h – parameter model is further simplified. Electronic Amplifiers

  25. Electronic Amplifiers

  26. Electronic Amplifiers

  27. Solution Electronic Amplifiers

  28. Electronic Amplifiers

  29. Electronic Amplifiers

  30. FET Amplifier Electronic Amplifiers

  31. AC Analysis Electronic Amplifiers

  32. Electronic Amplifiers

  33. FET Parameters Typical Values 500 kΩ 0.5 mS to 4 mS 80 to 200 Electronic Amplifiers

  34. Determining gm Electronic Amplifiers

  35. Example 7.8Calculate gm for a JFET with IDSS = 8 mA and Vp = 4 V, for dc bias point of (a) -0.5 V, and (b) -1.5 V Electronic Amplifiers

  36. AC Circuit Model of an FET Electronic Amplifiers

  37. AC Equivalent of FET Amplifier Electronic Amplifiers

  38. Negative sign means that the output is 180° out of phase. Electronic Amplifiers

  39. Maximum Voltage Gain : As Rac  Electronic Amplifiers

  40. Electronic Amplifiers

  41. This is much smaller than RS , hence it is completely bypassed. Electronic Amplifiers

  42. Electronic Amplifiers

  43. Review • Equivalent Circuit Method. • Hybrid Parameters. • Hybrid-πCircuit Model. • How Small is Small. • FET Parameters. • Determining gm. • AC Equivalent of FET Amplifier. • Maximum Voltage Gain Electronic Amplifiers

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