Digitally programmable MOS resistive circuit

Abstract

A mixed-signal cell is presented which operates as a digitally-controlled differential resistor and is suited to programmable continuous-time MOSFET-C filter applications. The cell is based on a digitally-controlled extension of the MOS resistive circuit (MRC) cell, in which digital tunability is obtained by embedding in the MRC transistors both the triode-region and switch functionalities, providing a compact implementation that preserves circuit performance. Post-layout simulation results for a 3-bit prototype in 0.8 /spl mu/m CMOS technology validate the feasibility of the proposed cell and its application to a digitally-tunable continuous-time MOSFET-C filter.