A low-power, programmable bandpass filter section for higher-order filter-bank applications

We present a programmable continuous-time bandpass filter with center frequencies ranging from 100 Hz to 10 MHz fabricated in 0.51 /spl mu/m CMOS processes operating at 3.3 V supply. This circuit is compact and low power (0.1 nW-15 /spl mu/W). SNR was 86 dB and 72 dB at 1 MHz for 2/sup nd/- and 4/sup th/-order sections with Qs up to 70 (4/sup th/-order). We fabricated a 6/sup th/- and 10/sup th/-order filter-bank chip. We present results for higher-order filters programmed at 1 MHz with Butterworth coefficients (passband ripple <0.5 dB).

I. Motivation for Low-power, Tunable Filters

With the increasing trend of designing power-efficient analog circuits for portable applications, the demand for analog filters with better performance in terms of speed and power consumption is high. Continuous time filters, particularly filters, are the most often used solution for signal frequencies of several MHz [1]. Irrespective of the frequency of operation, filters suffer from limited linearity, a large overhead of tuning circuitry and offsets due to device mismatch [2], [3]. In addition, traditional filter implementations based on OTAs are area-intensive, thus making them unsuitable for filter-bank applications.