Switched-Capacitor Equivalent of Some Active-RC Filters and a Novel Circuit
Sudhanshu Maheshwari and Iqbal A. Khan
This work presents conversion of active-RC filters to switched-capacitor ones, with the advantage of current-mode building blocks for better accuracy and frequency of operation, while migrating to sampled data approach for designing analog circuits. Two case studies are presented, each employing current feedback operational amplifiers. One circuit is based on two building blocks, while the other circuit employs single active building block. The simulation results are presented for varying signal frequency in the range of 5 KHz and up to 0.2 MHz. The clock frequency employed in different sets of results are 0.2 MHz and 2 MHz, which respectively correspond to lower and higher signal frequency. In order to cater to portable systems requirements, a fully CMOS compatible switched-capacitor filter circuit is then proposed, which is operable at ± 0.75 V, with 0.25 μm process. The same is tested with a maximum clock frequency of 10 MHz for 0.3 MHz signal with feasible capacitors of maximum 50 pF. All he results obtained are in good agreement with theory.
Keywords: Switched capacitor filters, current mode, analog signal processing