An operational amplifier circulator based on the weighted summer

A novel Y-circulator, constructed from operational amplifier (op-amp) weighted summers, consists of three op-amps and a few resistors and is integrable. It can be designed for three different or equal, complex or real, balanced or grounded terminations. The small leakage to the "isolated" port is caused by the finite common mode rejection of the op-amp and the sensitivity of the circuit to component deviations. One important merit of the new circulator is its ability to be designed for zero or finite gain, the gain-bandwidth product being, for a matched circulator, half that of the op-map. The circulator consists effectively of three "stages" or "active hybrid networks." Measurements confirm the analytical expectations. Finally, circuits are suggested for the use in the telephone set, at the ends of long distance telephone transmission circuits, in bidirectional repeaters, in filter connection, and in gyrator realization.