Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Poland
SYNCHROINFO JOURNAL. Volume 8, Number 1 (2022). P. 7-12.
In the paper, a general approach to noise analysis in continuous-time OTA-C filters is presented. Recently an increasing interest in the design of continuous-time filters based on the transconductance capacitor (OTA-C) technique has been observed. The operational transconductance amplifiers (OTAs) offer a higher bandwidth than their voltage-mode counterparts, can be easily tuned electronically, and have a better suitability for operating in reduced supply environment. Due to this, high frequency integrated filters are mostly realized as the OTA-C ones. Based on a matrix description of a general OTC filter topology, a universal formulas for evaluating the noise in any OTC filter are derived. The presented formulas can be easily implemented and used in computer-aided analysis/optimization software. The accuracy of the proposed method is confirmed by comparison with SPICE simulation. The example of application for finding the minimum-noise 5th order multiple-loop feedback filters implementing Butterworth and Bessel transfer functions is given.
Keywords: OTA-C filters, noise analysis, filter optimization.
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