Small singal amplifer. How to calculate

Discussion in 'Homework Help' started by Maintenance Man, Sep 19, 2011.

  1. Maintenance Man

    Thread Starter New Member

    May 12, 2010
    25
    0
    Hi to all
    Could someone please help me figure VE, IE, VRL and VCE of a small common emitter amplifier using a voltage divider as the input on base. I just would like to know the formuals. Thank you very much for your help.
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    For this diagram

    [​IMG]

    Base current is equal to :

    Ib = \frac{Vth - Vbe}{ Rth + (\beta+1)*Re}


    Vth = Vcc*\frac{R2}{R1+R2}

    Rth = *\frac{R1+R2}{R1*R2}

    And emitter current

    Ie = Ib*(\beta+1)

    Ve = Ie * Re

    Collector current

    Ic = Ib*\beta

    Vc = Vcc -  Ic * Rc

    Vce = Vc - Ve


    VRL ??

    The voltage gain is equal

    Av = \frac{Rc||RL}{re} = gm * Rc||RL  \approx 40 *Ic *(Rc||RL)

     re = \frac{Vt}{Ic} \approx \frac{26mV}{Ic}

     gm = \frac{1}{re} = \frac{Ic}{26mV} \approx 40 *Ic
     
    • 30.PNG
      30.PNG
      File size:
      7.3 KB
      Views:
      23
    Last edited: Sep 19, 2011
    anhnha likes this.
Loading...