Realization of all-pass transfer function using a differential amplifier

A class of active RC networks is presented with which an all-pass transfer function of arbitrary order, having simple negative real poles, has been realized by combining the output of a threeterminal RC network with a portion of its input in a differential amplifier. A synthesis procedure for such an all-pass function is also indicated. This class of networks has the advantage that the gain constant of the all-pass function may be varied by varying the gain of the differential amplifier.