On the design of optimal switched-capacitor filters based on the use of lossy frequency-dependent negative-resistance prototype structures

The authors introduce a new relatively stray-insensitive switched-capacitor filter (SCF) based on lossy frequency-dependent negative-resistance (FDNR) structures. The filter is derived by use of the lossless discrete integrator (LDI) and the backward-difference analogue-discrete (s-z) frequency transformations. An optimisation technique is used both to eliminate the distortion of the frequency response caused by the s-z transformations, and to deal with total capacitance minimisation-an important practical problem. The importance of these filter structures include their relative economy in realisation, leading to relatively low silicon utilisation compared with most standard SCF design techniques, and their very low sensitivity to parasitic capacitances.