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
    4,481
    1,264
    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

    Late Member

    Dec 26, 2010
    2,147
    302
    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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