hybrid model of transistor

Discussion in 'General Electronics Chat' started by raks_universe, Nov 17, 2009.

  1. raks_universe

    Thread Starter Active Member

    Mar 15, 2009
    67
    0
    our classes going on with hybrid model of transistor.i am including my class notes,pls clear my doubts in my basics.....

    consider CE circuit,

    the 4 variables are ib,ic,vb,vc.Among this ib and vc are taken as independent variable.
    //(DOUBT)why ib ,vc are taken as independent and why not vb and ic are taken as independent variable.pls tell me the reason ?(DOUBT)//

    continuing....

    vb=f1(ib , vc)
    ic =f2(ib ,vc)

    Making taylor series expansion,we get

    Δvb=(∂f1/∂ib) Δib + (∂f1/∂vc) Δvc
    Δic=(∂f2/∂ib) Δib + (∂f2/∂vc) Δvc
    //(DOUBT)why we are making taylor series expansion here...(DOUBT)//

    continuing...
    (∂f1/∂ib )= (∂vb/∂ib) = hie
    (∂f1/∂vc) = (∂vb/∂vc) = hre
    (∂f2/∂ib) = (∂ic/∂ib) = hfe
    (∂f2/∂vc) = ( ∂ic/∂vc) = hoe

    thus *vb = hie ib + hre vc*
    * ic = hfe ib +hoe vc*

    please solve my 2 doubts...............:confused:
     
  2. sudharshan.panduranga

    Active Member

    Apr 10, 2008
    61
    1
    Because Vb is depending on Ib and Ic is depending on beta and Ib.
    Ib and Vc 'll not change by any parameters,
     
  3. raks_universe

    Thread Starter Active Member

    Mar 15, 2009
    67
    0
    ib ,vc are taken as independent according to derivation

    When vb (input voltage)is increased ib will increase,so why can't we take vb as an independent variable.....

    And hence
    why cant we write as
    ib=(vb, vc)......
     
    Last edited: Nov 20, 2009
  4. raks_universe

    Thread Starter Active Member

    Mar 15, 2009
    67
    0
    reply
    pls.......
     
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