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Derivation of f T And f MAX In Bipolar And MOSFETs

Derivation of f T And f MAX In Bipolar And MOSFETs. C.-F. Huang 2004/04/10 National Taiwan University. Derivation of f T (MOSFETs). S → CE short. Derivation of f T (MOSFETs) (Continued). Assume the zero can be neglected. Derivation of f T (Bipolar). For Bipolar Transistors,.

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Derivation of f T And f MAX In Bipolar And MOSFETs

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  1. Derivation of fTAnd fMAXIn Bipolar And MOSFETs C.-F. Huang 2004/04/10 National Taiwan University

  2. Derivation of fT(MOSFETs) S → CE short

  3. Derivation of fT(MOSFETs) (Continued) Assume the zero can be neglected.

  4. Derivation of fT(Bipolar) • For Bipolar Transistors, CDE is due to minority carriers caused by FB

  5. Derivation of fT(Bipolar) (Continued) QE = minority holes stored in emitter QB = minority electrons stored in base QBE = electrons induced by the current through the depletion region of BE-junction QBC = electrons induced by the current through the depletion region of BC-junction

  6. Derivation of fT(Bipolar) (Continued) Width of Neutral Region Width of Depletion Region if drift current is considered. is greater than because of reverse-biasing.

  7. Derivation of fT(MOSFETs) (RS and RD are included)

  8. Derivation of fT(MOSFETs) (Continued)(RS and RD are included) Miller’s Theorem

  9. Derivation of fT(Bipolar) (RS and RD are included) • For bipolar, the result is similar. • The only difference is that the term must be included.

  10. Derivation of fMAX(MOSFETs)

  11. Output and Input Impedance For high frequency, Rg is independent of RL

  12. Derivation of fMAX(MOSFETs)(Continued) For the matching conditions,

  13. Derivation of fMAX(MOSFETs)(Continued) See p.3

  14. Derivation of fMAX(Bipolar) For bipolar transistors, there is no term.

  15. Derivation of fMAX(MOSFETs)(Continued)(RS and RD are included) For high frequency condition, Cgs → short Replace Rg by Rg+Rs w/ (RS+RD) term w/o (RS+RD) term

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