A 20-Msample/s switched-capacitor finite-impulse-response filter using a transposed structure

Abstract

A programmable four-tap analog finite-impulse-response filter for use in a decision-feedback equalizer has been realized in a 2-/spl mu/m double-poly CMOS process. It uses a modified transposed structure and double sampling to minimize power dissipation. Also, it uses programmable-gain sample-and-hold amplifiers with a constant feedback factor, input capacitance, and load to reduce the performance variation as a function of programming. The filter is fully differential, occupies an active area of 11.8 mm/sup 2/, and dissipates 56.5 mW.