beta dc

Discussion in 'Homework Help' started by amaresh92, Jan 1, 2011.

  1. amaresh92

    Thread Starter New Member

    Oct 31, 2010
    23
    0
    calculate alpha DC (emitter to collector dc current gain) and beta DC (base to collector dc curent gain) for a transistor which has Ic=2.5ma, Ie=2.6ma .





    formula 1) alpha DC=Ic/Ie.
    formula 2) beta DC =Ic/Ib.
    formula 3) beta DC = alpha DC/(1-alpha DC)
    formula 4) Ib=Ie-Ic






    alpha dc=Ic/Ie

    =2.5/2.6
    =0.96


    Ib=Ie-Ic

    =2.6-2.5
    =0.1ma


    using formula 2)

    beta DC =Ic/Ib

    =2.5/0.1
    =25

    using formula 3)

    beta DC = alpha DC/(1-alpha DC)

    = 0.96/(1-0.96)

    =24



    my doubt is, from above calculation for beta DC using formula 2 and 3 we are getting two different values for beta DC. so which one is correct and under which condition or how i should use these two formula? In the sense when i should use formula 2 and formula 3.

    advanced thanks
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    You should be posting in the homework forum - correct?
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You should get the same answer. If you round beta DC to 5 decimal places you will get the same answer.
     
  4. amaresh92

    Thread Starter New Member

    Oct 31, 2010
    23
    0
    i am really beg pardon for my blunder mr. marshallf3.
    hence after it would not be repeated.
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    I think it's a problem with alpha rounding, not with beta rounding. Beta is 25.0000, so rounding isn't an issue.
     
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