                      ----------------Vcc
                      |
                      R2
                      |
                     RFC
                      |
                      |---C2-------X3- O/P
                      |      |   |
              G |-----| D    |   |
I/P----X1-------|            |   |
           |    |-----| S    R3  X4
           |          |      |   |
           |      ----|---   |   |
          X2      |   |   |  |   |
           |     Cd   R1 Cd  |   |
           |      |   |   |  |   |
  ------------------------------------ Earth  
