Cascadable low voltage operated current-mode universal biquad filter

Abstract

A new current-mode universal biquad filter structure using two Z-Copy Current Follower Transconductance Amplifiers (ZC-CFTAs), and two grounded capacitors is proposed in this paper. The proposed structure can be configured into either multiple inputs multiple outputs (MIMO) or multiple inputs single output (MISO) configurations. In each configuration, the proposed circuit can realize all the standard filtering responses such as low pass (LP), band pass (BP), high pass (HP), band reject (BR), and all pass (AP), by choosing the current input/output terminals appropriately. The circuit operates at lower supply voltage rails, and for response realization it does not require inverted current input signal(s) and component matching constraints. The proposed circuit offers an advantage of electronic tunability of pole-frequency independent to the quality factor. The effort is further extended to originate an Nth- order LP filter, through direct cascading of proposed circuit blocks. Performances of the proposed circuits were examined through P-SPICE programs on cadence tools using standard CMOS technology.