A non-uniform sampling approach for the reduction of capacitance spread in SC circuits

In this paper, an effective approach to the design of large time constants implemented with switched-capacitor (SC) techniques for use in low-frequency signal processing applications, is presented. The proposed method utilizes a non-uniform sampling scheme, which adds one degree of freedom in obtaining the time constant of SC integrators. As a result, capacitor spread and total capacitor area are reduced and, hence, silicon area can be minimized. To prove the feasibility of the presented approach, the design and the implementation of a second-order lowpass notch SC filter are discussed. Experimental results from a 0.35-mum CMOS test-chip that operates at 2 kHz sampling frequency are presented