D-MRC: digitally programmable MOS resistive circuit

This paper presents the D-MRC circuit, a mixed-signal cell which operates as a digitally-controlled differential resistor, and that is suited to programmable continuous-time MOSFET-C filter applications. The cell is based on a digitally-controlled extension of the MRC (MOS Resistive Circuit) cell, in which digital tunability is obtained by embedding in the same MRC transistors both the triode-region and switch functions, providing a compact implementation that preserves circuit performance. This cell is of interest for static and dynamic reconfigurability of mixed-signal circuits, as required in multistandard wireless CMOS receivers. The proposed cell has been designed down to the layout level for a particular prototype with 3-bit digital controllability in 0.8 μm CMOS technology. Post-layout simulation results validate the functionality of the proposed cell and its application to a digitally-tunable continuous-time MOSFET-C filter