A comparison of active, multiple-loop feedback techniques for realizing high order bandpass filters

This paper reviews and compares the four multiple-loop feedback techniques used to realize high-order narrow-band filters; namely: follow-the-leader feedback (FLF), primary resonator block (PRB), leapfrog (LF), and modified leapfrog (MLF) techniques. The comparison is based upon the following criteria: design ease and flexibility, sensitivity performance, insensitivity to design errors due to nonideal operational amplifiers, and tunability. In all comparisons the simple but highly sensitive cascade technique is used as a reference. Several examples are cited which indicate comparative trends in sensitivity performance. Finally the computer program used to realize minimum sensitivity FLF networks is described.