A 10.7-MHz sixth-order SC ladder filter in 0.35-/spl mu/m CMOS technology

A sixth-order 10.7-MHz bandpass switched-capacitor filter based on a double terminated ladder filter is presented. The filter uses a multipath operational transconductance amplifier (OTA) that presents both better accuracy and higher slew rate than previously reported Class-A OTA topologies. Design techniques based on charge cancellation and slower clocks are used to reduce the overall capacitance from 782 down to 219 unity capacitors. The filter's center frequency and bandwidth are 10.7 MHz and 400 kHz, respectively, and a passband ripple of 1 dB in the entire passband. The quality factor of the resonators used as filter terminations is around 32. The measured (filter + buffer) third-intermodulation (IM3) distortion is less than -40 dB for a two-tone input signal of +3-dBm power level each. The signal-to-noise ratio is roughly 58 dB while the IM3 is -45 dB; the power consumption for the standalone filter is 42 mW. The chip was fabricated in a 0.35-/spl mu/m CMOS process; filter's area is 0.84 mm/sup 2/.     

A 60-mW 200-MHz continuous-time seventh-order linear phase filter with on-chip automatic tuning system

A full CMOS seventh-order linear phase filter based on g/sub m/-C biquads with a -3-dB frequency of 200 MHz is realized in 0.35-/spl mu/m CMOS process. The linear operational transconductance amplifier is based on complementary differential pairs in order to achieve both low-distortion figures and high-frequency operation. The common-mode feedback (CMFB) employed takes advantage of the filter architecture; incorporating the load capacitors into the CMFB loop improves further its phase margin. A very simple automatic tuning system corrects the filter deviations due to process parameter tolerances and temperature variations. The group delay ripple is less than 5% for frequencies up to 300 MHz, while the power consumption is 60 mW. The third-harmonic distortion is less than -44 dB for input signals up to 500 mV/sub pp/. The filter active area is only 900 /spl times/ 200 /spl mu/m/sup 2/. The supply voltages used are /spl plusmn/1.5 V.