Study On Continuous Time OTA-C Active Filter

The research on the fully integrated continuous-time filter is a frontal field ofthe circuits and system in the world. The continuous-time filter has been appliedwidely in communications and signal processing. The fully integrated continu-ous-time filter can make the whole system work more stably and reliably.In the paper, the international and national researches and development trendsof the fully integrated continuous-time filter is systematically summarized. Theprinciple and application of the high-performance operational transconductance am-plifier is analyzed. The concrete method designing active filters with operationaltransconductance amplifier (OTA) is lucubrated. The programmable operationalTransconductance amplifier (POTA) has realized the program control of the con-tinuous-time OTA-C filter, and the simulation has obtained a good result.The paper has analyzed the basic structure of MOS transistor and analogue in-tegrated circuit unit component by MOS transistor such as basic current source andthe source coupled differences pairs. The construct design and application of CMOSoperational transconductance amplifiers have been studied widely and deeply in thethesis. Firstly, we compare several improved structures of OTA after analyzing thesource coupled differences pairs. Secondly, the paper is mainly concerned withsecond-order filter, and a voltage model OTA-C multifunction second-order filter isdesigned. Simulation results have shown that the circuit can realize four kinds offilter of low pass, high pass, band-pass and band stop. The design methods of cas-cade connection are discussed in detail. We give the theoretical derivation and de-sign method. Although each circuit system is different, they all constitute by OTAand capacitance. The circuit is simple and easy to integrate and be compatible withCMOS large-scale integration circuit. The design example is given. Finally, the de-sign strategy of the programmable operational transconductance amplifier (POTA) isproposed based on digital potentiometers AD8403and OTA circuit. Examples of thefilters are presented respectively. Simulation results have shown that this method canrealize the programmability of analog filter.