Deriving technique of equivalent forms from general filter circuits and its application

In the active circuit design it is necessary to consider the designed filte r features of the number of elements, element value spread, element sensiti vities, and the circuit structure. For example, the desirable circuit struc ture of the operational transconductance amplifier-C (OTA-C) filter is that all the elements are of equal or near equal value and all the capacitors a re grounded. Thus, it is important for the filter design to find the useful method to derive such a desirable equivalent structure. This paper describ es the necessary and sufficient condition and a practical procedure to deri ve an equivalent form from a general active RC circuit or a general LCR cir cuit. The design examples deriving equivalent voltage controlled current so urce (VCCS)-C or VCCS-RC circuits from the third-order low-pass LC filter a re demonstrated, By this technique it is possible to derive the suitable eq uivalent circuit for the implementation.