Multi-loop high-order filter structures using operational transconductance amplifiers (OTAs) and capacitors are investigated. An approach based on the micromodel combination is presented. This method is convenient to analyze given OTA-C filters and to generate new OTA-C circuit structure. The micromodels as basic building blocks of OTA-C filters consist of some previously reported and other new units. They are implemented to use OTAs as their active components and at most one capacitor as their passive component. A new OTA-C filter structure with chain-like form is derived. A variety of features can be realized by selecting proper inputs and outputs from the same network. As an application of the method, a three order bandpass filter is designed. SPICE simulation shows the approach available.
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