Ultra low power automatic tuning for gm-C filters

A simple technique for on-chip tuning of ultra low power Gm-C filters is analyzed in this paper. The technique locks the filter G_m/C2_π frequency to an external reference clock. The proposed tuning method is tested with a low frequency first order high pass section. The tuning of this filter for different applications by changing the reference frequency is also explored. The circuit tunes the filter frequency in a range from 10 Hz to 200 Hz with a consumption of less than 800 nA.