FREQUENCY RESPONSE / NORMALISATION AND FILTER CIRCUITS
Passive Band Pass Filter

figure V : passive band pass filter

          ,        

   ,   

for S = jw, and because S2 = -w2    =>                  

            =>           

                     

K is the DC gain which is set equal  to unity for simplicity.  

The roots of the denominator should be real and different for each other  in order for the band pass filter to maintain its characteristics.  In order to do so, the Q factor should be greater than 0.5.         

 .....(A)

    transfer function

The amplitude would be :

  

or relating to decibels of loss :

....(B)  ....(C)

         amplitude response                          phase response

figure W : bode plots of second order BPF