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.