nth‐Order Analog All‐Pass Filters Using a Single Op‐Amp

ABSTRACT In this paper, we present a scalable design methodology to realize th‐order voltage‐mode all‐pass filters (APFs) that realize a prescribed constant group delay using a single operational amplifier (op‐amp) and a grounded impedance element. The proposed approach enables higher order filter implementations by simply varying the structure of the grounded impedance network, without requiring additional active elements. We provide the transfer functions of the first five orders and show that they correspond directly to the Padé approximation of an ideal delay, providing a systematic design methodology for a target group delay . The proposed circuits are verified through experimental measurements and SPICE simulations, demonstrating excellent agreement with the theoretical predictions.