/*

  Program:  kqm_to_n.c                               Revision:  21-JULY-2006
            ----------


  Differential Amplifier Low Pass Filter Calculation Program   step #1


  This program ask for you to enter three parameters:

     The pass-band gain of the filter  "K"  which is equal to   R2/R1

     The "Q" of the filter, which is:  0.707 for Butterworth,  0.577 for Bessel

     The value "m"  where  R2 = R  and  R3 = mR


  The program then outputs the value "n"  where  C1 = C  and  C2 = nC

  This program is setup to provide the values for differential Low Pass
  filters and it assumes that the gain "K" is always positive.

  The equation is:


          [ Q (1 + m(K+1))] **2
    n =  -----------------------
                 2m


  Refer to  TI  sloa_054  documentation about fully differential amplifiers.

*/



#include <stdio.h>
#include <math.h>

#define     PI       3.1415926

main ()

{
        float   K   ;     /*  the pass-band gain of the filter  */

        float   Q   ;     /*  the required Q of the filter pole pair  */

        float   m   ;     /*  the value where  R2 = R  and  R3 = mR   */

        float   n   ;     /*  the value where  C1 = C  and  C2 = nC   */

        float   temp_1, temp_2, temp_3, temp_4, temp_5    ;



        printf(" \n ");
        printf("Enter the required pass-band gain of the filter K,    \n");
        printf("       the required quality of the filter Q,  and     \n");
        printf("       m where m is defined as  R2 = R  and  R3 = mR  \n");
        printf(" \n ");

        printf("      Enter the filter gain \"K\" : ");
        scanf( "%f", &K )    ;
        printf(" \n ")          ;

        printf("      Enter the filter quality \"Q\" : ");
        scanf( "%f", &Q )  ;
        printf(" \n ")          ;

        printf("      Enter \"m\"  where  R2 = R  and  R3 = mR : ");
        scanf( "%f", &m )     ;
        printf(" \n ")          ;


        printf( "\n The filter gain \"K\" is = %7.3f \n",
                K )  ;

        printf( "\n The filter \"Q\" is = %7.3f \n",
                Q )  ;

        printf( "\n The resistor ratio \"m\" (where R3 = mR) is = %7.3f \n",
                m )  ;




        temp_1 =  Q * (1.0 + ( m * ( K + 1.0 ) ) )  ;

        temp_2 =  temp_1 * temp_1                   ;

             n =  temp_2 / ( 2 * m )                ;


       printf( "\n The capacitor ratio \"n\" (where C2 = nC) is = %7.4f   \n",
               n ) ;

}