Design of Low-Power Low-Area Tunable Active RC Filters

A method to design low-power low-area active RC filters is presented. The output voltages of the operational amplifiers are scaled and buffered, allowing the use of single stage topologies for less power consumption and eliminating the compensation capacitor. Tuning of the filter characteristic is also done by switching the currents through the output buffers, which removes the need for capacitor banks. The advantages of the proposed method are incorporated to present a general low-power biquad with small die area. The biquad section is then used to design a low-power baseband filter for Bluetooth receivers with 600-KHz cutoff frequency. The fourth-order filter, fabricated in a 0.18-μm CMOS process, consumes 0.5 mW with a die area of 0.13 mm
²
.