1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Thevenin equivalent

  1. Sep 10, 2014 #1
    1. The problem statement, all variables and given/known data
    I'm trying to understand where the (β+1) comes from.

    2. Relevant equations


    3. The attempt at a solution



    Attached Files:

  2. jcsd
  3. Sep 10, 2014 #2


    User Avatar

    Staff: Mentor

    Welcome to the PF.

    Without seeing the original circuit that this is modeling, it's hard to be sure. But for a CE BJT amplifier, your collector current Ic = β * Ib. So your emitter current is.....
  4. Sep 10, 2014 #3
    i've attached the solution that i have in the book, the value of beta is 150 and R1=100k and R2=39k, the only problem I have is that how do you get to the vth while substituting beta and the resistance in both sides to be equal to -Beta (-is/beta+1), the beta + 1 has to come out from simplying and combining like terms but I just can't see it.
  5. Sep 10, 2014 #4


    User Avatar

    Staff: Mentor

    So factor out the i in that equation above:

    (β + 1)i + is = 0

    There's your (β + 1) term.

    That doesn't look right. You want to substitute for i in your equation for Vth from above, but what you've stuck in there also contains i.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted