A Compact First-Order Mixed-Mode Multifunction Filter Architecture Using CFDITA

Abstract

A first-order mixed-mode multifunction filter utilizing a Current Follower Differential Input Transconductance Amplifier (CFDITA) and a grounded capacitor is introduced in this paper. It can be configured to provide first-order high-pass (HP), low-pass (LP) and all-pass (AP) responses in current-mode as well as a HP response in transadmittance-mode. The filter offers advantages such as suitable impedances in both current-mode and transadmittance-mode, facilitating simple cascadability in either mode, ease of integration, minimal use of active and passive components, explicit current outputs to drive current-mode devices and the employment of a grounded capacitor that assists in parasitic absorption of the active element used. Additionally, it has a higher operating frequency (10.3 MHz), low power consumption (1.5 mW), electronic tunability of pole frequency and no need for matching passive components. A thorough analysis considering ideal, non ideal, and parasitic effects is provided. The study also examines the use of the suggested filter as a quadrature oscillator. Post-layout simulations utilizing the Cadence Virtuoso tool with a 180 nm GPDK (Generic Process Design Kit) technology have confirmed the developed circuits. The layout of CFDITA measures an area of 28.4 µm × 26.5 µm.