A Single-Ended and Fully-Differential Universal Current-Mode Frequency Filter with MO-CF and DACA Elements

Abstract

The paper presents proposal of the 2nd-order universal frequency filter. The presented filter operates in the current-mode and it is designed in the single-ended and fully-differential form. Signal-flow graphs (SFG) method has been used in the proposal. The proposed filter is employing multi-output current followers (MO-CFs) and digitally adjustable current amplifiers (DACAs) as active elements. The pole frequency of the filter can be controlled without disturbing its quality factor. Functionality of the proposed filter in both S-E and F-D form has been verified by PSpice simulations using available models of used active elements and also by experimental measurements. A comparison of simulation and experimental results of the S-E and F-D form of the presented filter is made. Subsequently, a comparison of experimental results of both forms of the filter is also included.

Keywords

• active filters
• analog circuits
• current-mode circuits
• differential amplifiers
• frequency control