Programmable floating-gate second-order sections for Gm-C filter applications

We present programmable, fully-differential G/sub m/-C second-order sections showing tunability over a wide range of frequencies. The second-order sections use a floating-gate operational transconductance amplifier (FG-OTA) to realize tunability. We present experimental results showing frequency- and Q-tuning for a lowpass (LPSOS) and a bandpass second-order section (BPSOS) designed using these FG-OTAs. Measured 1-dB compression for LPSOS and BPSOS are -15 dBm and -11 dBm, respectively. The presented circuits are fabricated in a 0.5 /spl mu/m n-well CMOS process available through MOSIS.

I. Continuous-Time Filters

Continuous-time filters are an important part of analog signal processing systems operating at high frequen-cies. Although switched-capacitor filters realize accurately the quality factor, , and the time constants using capacitor ratios, problems such as high dynamic power make them impractical to use at higher frequencies. Issues such as offset due to mismatch, linearity and tunability make the continuous-time filters cumbersome and unattractive to use at lower frequencies. Irrespective of the frequency of interest, filters require additional circuitry to tune the filter to get the desired response [1], [2].