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(m)-C biquads with a -3-dB frequency of 200 MHz is realized in 0.35-mum 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(PP). The filter active area is only 900 x 200 mum(2). The supply voltages used are +/-1.5 V. Index Terms-Automatic tuning systems, common-mode feedback circuits (CMFB), continuous-time filters, linear operational transconductance amplifiers.