Accurate SI filters using RGC integrators

The design and implementation of single-ended and fully-differential switched current (SI) biquadratic high-Q bandpass filters to meet the specifications of the dual-tone multiple-frequency (DTMF) system are presented. Both designs use the regulated-gate cascode (RGC) dynamic current mirror to obtain center frequency accuracy of 0.1% and a quality factor of 24. Compared to the equivalent switched capacitor (SC) implementation of these filters, the single-ended SI filter requires 30% less area for the same minimum-sized capacitance, power dissipation and performance.<
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