Digitally programmable high-order current-mode universal filters

New high-order current-mode (CM) filter topologies capable of providing all functions simultaneously are presented. The proposed filters are based on digitally controlled current amplifiers and unity gain voltage buffers. The gains of the current amplifiers are digitally programmed to adjust the filters’ transfer function coefficients. It is shown that the proposed approach results in more efficient realizations compared with its counterparts based on other CM active elements. Using BSIM3 0.18 μm CMOS models, simulation results of a fourth-order universal filter are provided.