common emmiter-feedback resistor small signal analysis

Discussion in 'Homework Help' started by mohammad.khatib, Aug 2, 2010.

  1. mohammad.khatib

    Thread Starter New Member

    Aug 2, 2010
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    hey all please help me with the (common emmiter-feedback resistor small signal analysis) i need the derivation of Rin and Ro and the gain pleasee
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    You need to create small signal model of a amplifier and then find the unknown.
    2.PNG

    For example voltage gain is equal :
    Au = Vout/Vin
    Vin = Ib*H11 + Ie *Re
    Ie = Ic + Ib = (hfe+1)*Ib
    Vin = Ib*H11 + (hfe+1)*Ib *Re = Ib*(h11 + (hfe + 1)*Re)
    Vout = -Ic*Rc = -Ib*hfe*Rc

    Au = - ( Ib*hfe*Rc ) / ( Ib*(h11 + (hfe + 1)*Re) = - ( hfe*Rc ) / (h11 + (hfe + 1)*Re)
    And h11 = (Hfe +1) * re = (Hfe +1) * 26mV/Ic

    To find Rin you need to find
    Rin = Vin /Iin
    Rout = Vout/Iout
     
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