An inaccuracy?

Discussion in 'Feedback and Suggestions' started by Skfir, Sep 25, 2014.

  1. Skfir

    Thread Starter Active Member

    Aug 19, 2010
    135
    4
    http://www.allaboutcircuits.com/vol_3/chpt_4/10.html

    Hi guyz! So I am a bit perplexed. On that page there is a passage on base bias calculations and it is written there : "Silicon small signal transistors typically have a β in the range of 100-300. Assuming that we have a β=100 transistor, what value of base-bias resistor is required to yield an emitter current of 1mA?

    Solving the IE base-bias equation for RB and substituting β, VBB, VBE, and IE yields 930kΩ. The closest standard value is 910kΩ." I was wondering why 910k and then it is written, that Vbb was 10v. But the thing is, it is written nowhere above about 10v! The battery on the picture also doen't have any voltage on it, so it seems that the 10v value just falls from the sky. So could you please add some reference to this voltage before the equation.
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    V_{BB} is given along with the set of equations in the picture right after the sentence you quoted. However, yes, I agree that it could be set before it.
     
  3. Skfir

    Thread Starter Active Member

    Aug 19, 2010
    135
    4
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