Automatic tuning circuit for Gm-C filters

This paper presents a CMOS on-chip automatic tuning circuit using phase lock loop (PLL) technique for continuous-time Gm-C filters. In the tuning circuit, to achieve the maximum tuning accuracy, the new VCO architecture that generates precisely fully differential clock swings and keeps the absolute oscillation in all operating condition was proposed. Measured results show that the designed automatic tuning circuit is suitable for the continuous-time Gm-C filter. The verified system is fabricated in a 0.18 mum CMOS technology and consumes 2.78 mW at a 1.8V supply voltage.