Nano-scale area-efficient Gm–C filters using MOS capacitors

Abstract

ABSTRACTThe rapid growth of scaling and integration of nano-scale digital circuits is hardly tracked by the analog circuits which require additional passive components for fabrication. Mixed-signal Complementary Metal Oxide Semiconductor (CMOS) technologies are released with some delays after digital CMOS technologies, due to the issues related to integration of analog components. This urges the designers to consider using the same digital CMOS technology for integration of advanced analog circuits like continuous-time filters. As such, this article presents an area-efficient Gm–C filter made from MOS devices only. Instead of classical metal–insulator–metal capacitors, the proposed filter exploits the available compact-size MOS devices as capacitor. This modification makes the filter design compatible to any low-cost digital CMOS process. Besides, the 3-dB cut-off frequency of the filter can now be changed by varying the size of MOS capacitors. The effectiveness of the new design approach is validated through simulation of a fifth-order elliptic low-pass filter with a cut-off frequency of 1 MHz in 90-nm CMOS technology. The new filter dissipates around 115 µW from a 1.0 V power supply, and the sensitivity of its cut-off frequency is kept as low as 6% over various process and temperature corners.