help with analysing a bjt ..

Discussion in 'Homework Help' started by herbgriffin, Feb 18, 2011.

  1. herbgriffin

    Thread Starter New Member

    Feb 14, 2011
    are the values of dc currents in a transistor different in ac analysis of the is the value of Ib cannot be used in ac analysis..also how to get the value of beta if you are given min to max...thank you in advance..
  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    The bias conditions in an amplifier are often considered in a DC analysis, while AC methods and small-signal analysis may treat signal amplification. One way of representing conditions in circuits uses capital letters to denote quiescent or DC conditions (Ic, Ib), and lower-case variables (ic, ib) for incremental or AC variations. If that is what you are referring to, yes, you need to avoid mixing these things up.

    It is harder to see what you mean in your question about how to "get the value of beta if you are given min to max". The whole point is that one cannot be sure of the value. For this reason, circuits should be designed to be tolerant to variations in beta. Feedback biasing circuits and negative feedback in amplifiers are among etechniques used to address this issue.
    Last edited: Feb 19, 2011