The Design Of Fully Integrated Continuous Time Filters

Continuous-time filters are wilderly used in telecommuniation and signalprocessing systems. The system can be made to work more stable and reliable by usingfully-integrated continuous-time filters. This dissertation is concerned with the design offully integrated continuous-time filters. Three design methods are given. Firstly, in the lower frequency application, R-MOSFET-C filter is used. They areeasy to implemente with operational amplifier blocks while maintaining closearchitectural similarities to an active RC filter. These R-MOSFET-C filters,implemented in a standard CMOS process, utilize the linearized model behavior of anMOS transistor operating in the triode region instead of a passive resistor. Throughtuning the grid-voltage of MOS transistor, we can tune the equivalent resistance,accordingly tuning the cut-off frequency of the filter. A R-MOSFET-C filter designmethod is proposed and an example is presented in the dissertation. Simulation resultconfirms its performance similar to that of active RC filter. Secondly, for the high frequency application, a late-model device of operationaltransconductance amplifier is introduced. The design strategy of OTA is proposed andthe OTA parameters are given. Based on this design, the procedure of how to convert apassive RLC filter to active OTA-C filter is described. In the presented example, thedesigned OTA is used and the OTA's transconductance is tested. Simulation resultshows that the OTA-C filter has same performance with RLC ladder filter. The cut-offfrequency of the filter is tuned by tuning its bias current. Finally, the tuning of the filter is studied and the multiple loop feedback topologyis discussed in detail. After the introduction of IFLF OTA-C filter, a fifth-order IFLFOTA-C filter is designed. Because of the imprecise of components, these filters need tobe tuned. There are two kinds of tuning method, dirtect tuning and indirtect tuning. Inthis thesis, the peak detection tuning is studied. The Simulation result shows that IFLFOTA-C filter meets the requirements of the design.