Ratio gain & dB conversions

Discussion in 'Homework Help' started by notoriusjt2, Nov 3, 2010.

  1. notoriusjt2

    Thread Starter Member

    Feb 4, 2010
    209
    0
    Convert the ratio gain A = vout / vin = 1.14 to dB

    dB=20 log (Vo/Ein)
    dB=20 log (1.14)
    dB=1.138

    can dB really be exactly the same as the ratio gain here?


    then


    Convert the voltage gain A = - 1.37 dB to ratio gain.

    the only equation listed in my textbook that has Av in it is this one

    -3dB = 20 log (Av)

    but its not possible to log a negative number. what equation am I supposed to use?
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Looks like it.

    What you have is the 'intersection' of two functions

    y=Av and y=20log(Av)

    consider the functions

    y=x and y=x^2 which have the same value when x=1


    Av[dB]=-1.37dB

    Av=10^(Av[dB]/20)=10^(-0.0685)=0.854
     
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