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Nowadays I am working on bjt transistor ac analysis. I use r(e) model for bjt transistors ac analysis in my university. I know there are separate methods for low frequency medium frequency high frequency in Bjt Transistors. I have read in some comments that the re model does not correspond to real physical values. Transistors - What is re model? see LvW 's comment. What is the most realistic model I should use if I want to work on ac analysis of medium frequency bjt transistors (amplifier design etc.)?

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    \$\begingroup\$ Can you show us how r'e model looks like? Do you mean T-model? ittc.ku.edu/~jstiles/412/handouts/… (page 55?) The Hybrid-Π and the T circuit models are equivalent they both will result in the same correct answer! \$\endgroup\$
    – G36
    Apr 3, 2020 at 22:39
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    \$\begingroup\$ @G36 that handout you linked is surprisingly good. It also contains the answer to the OP question at page 57: "The Hybrid-Π and the T circuit models are equivalent—they both will result in the same correct answer!". The OP is confused because LvW has a dogmatic view "voltage cause current" that makes him think that there is only one true and sacred way to model a transistor. \$\endgroup\$ Apr 3, 2020 at 23:23
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    \$\begingroup\$ Yes this model is useful, I use it here electronics.stackexchange.com/questions/489944/… @LvW had in mind that this model does not show how a BJT's work in a physical way. The BJT in the active region behaves just like a voltage-controlled current source. The collector acts like a current source whose current is determined by the base-emitter voltage ( transconductance device) electronics.stackexchange.com/questions/302832/… \$\endgroup\$
    – G36
    Apr 3, 2020 at 23:25
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    \$\begingroup\$ But the re-model does not show it but it will give you the correct answer. \$\endgroup\$
    – G36
    Apr 3, 2020 at 23:28
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    \$\begingroup\$ @SredniVashtar Yes, indeed this handout is very good. I hope that the OP will read it whole because it's worth it. \$\endgroup\$
    – G36
    Apr 3, 2020 at 23:36

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