Design of fully adjustable solution of band-reject/all-pass filter transfer function using signal flow graph approach

The main aim of this paper is to show logical method how to obtain fully electronically adjustable active filter with electronic control of type of the transfer function without any change of topology and change of input excitation or reconnection of output. It is important for on-chip applications especially. Results of synthesis are demonstrated on biquadratic filter (band-reject and all-pass response) structure and two equivalent solutions are introduced and discussed. Achievable features are confirmed by PSpice simulations.