High-selectivity switched-capacitor bandpass filter with quasi-continuous quality factor tunability
This paper describes the design and implementation of a second-order switched-capacitor (SC) bandpass (BP) filter with very wide quality factor (Q) programmability range. The filter selectivity is digitally programmed by varying the effective sampling frequency of an SC branch, without modifying any capacitor value. The proposed approach allows a quasi-continuous Q-factor tunability avoiding, in principle, the inherent quantization error associated to any traditional programming technique. Automatic Q-factor tuning is performed by using a scheme based on an amplitude-locking loop approach. Experimental results obtained from a 0.8-mum CMOS integrated prototype demonstrate the versatility of the proposed technique for high-Q SC BP filters.
bandpass filters cmos analog integrated circuits switched-capacitor circuits