Finding Rout and Rin

Discussion in 'Homework Help' started by matlark, Dec 6, 2008.

  1. matlark

    Thread Starter New Member

    Dec 6, 2008
    8
    0
    Hello,
    What is the method of finding Resistance out and Resistance in for any of the BJT variations? Thanks
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    There are two different resistances to be considered for transistors and generally active devices, the DC resistance and the AC or incremental resistance. The DC resistance equals the DC voltage divided by the DC current. The AC resistance is a different concept and it depends on the bias point of the transistor. Generally, the impedance looking into the base of the transistor equals

    Zb=25mV/Ib

    and the impedance looking into the emitter of the transistor is

    Ze=25mV/Ie

    where

    Ib=DC bias current through the base
    Ie-DC bias current through the emitter
     
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