CE amplifier gain question

Discussion in 'Homework Help' started by ECE101, Dec 12, 2011.

  1. ECE101

    Thread Starter New Member

    Nov 25, 2011
    29
    0
    Hi,

    I'm just looking to verify something

    [​IMG]


    From a mathematical point of view:

    Gain = -gm*Rc

    gm = Ic1/Vt
    Rc = 8k

    When Vo = +15

    AV = -((15/8*10^3)/25*10-3) * 8*10^3
    = -600


    When Vo = -10

    AV = ((10/8*10^3)/25*10-3) * 8*10^3
    = 400



    Is this correct?


    note to mods:

    I posted this thread here: http://forum.allaboutcircuits.com/showthread.php?t=63201 however I think it belongs in Homework help.
    If you could delete/merge the other one that would be great.
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    Your answer is wrong.

    The voltage gain is equal to:

    AV = Rc * \frac{ gm}{ gm * Re||R3 + 1 }\approx \frac{Rc}{Re||R3}
     
    ECE101 likes this.
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Note also that Vout swings up and down because Ic varies, not Rc. Correcting for this will lead to a completely different answer to your present one.
     
    ECE101 likes this.
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