Slawomir Koziel,
Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Poland

DOI: 10.36724/2664-066X-2022-8-1-7-12

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.


[1] R. Schaumann, M. S. Ghausi, and K. R. Laker, Design of Analog Filters, Passive, Active RC, and Switched Capacitor. Englewood Cliff, NJ: Prentice-Hall, 1990.

[2] T. Deliyannis, Y. Sun, and J. K. Fidler, Continuous-time active filter design, CRC Press, USA, 1999. [3] R. L. Geiger and E. Sánchez-Sinencio, „Active filter design using operational transconductance amplifiers: A tutorial,” IEEE Circuit and Devices Mag., vol.1, pp.20-32, 1985.

[4] B. Nauta, Analog CMOS filters for very high frequencies, Kluwer Academic Publishers, 1993.

[5] Y. Sun (Editor), Design of high frequency integrated analogue filters, The Institution of Electrical Engineers, London, 2002.

[6] Y.P. Tsividis, “Integrated continuous-time filter design – an soverview”, IEEE J. Solid-State Circuits, vol.29, pp.166-176, 1994

[7] A. Brambilla, G. Espinosa, F. Montecchi, E. Sánchez-Sinencio, ”Noise optimization in operational transconductance amplifier filters,” in Proc. Int. Symp. Circuits Syst. ISCAS, Vol.1, pp. 118 -121, 1989. [8] G. Ejthivoulidis, L. Toth, Y.P. Tsividis, „Noise in Gm-C Filters”, IEEE Trans. Circuits Syst., Vol. 45, No. 3, pp. 295-302, Mar. 1998.

[9] S. Koziel, S. Szczepanski, „Dynamic Range Comparison of Voltage-Mode and Current-Mode State-Space Gm-C Biquad Filters in Reciprocal Structures”, IEEE Trans. Circuits Syst.-I, Vol.50, No.10, pp.1245-1255, Oct.2003.

[10] Y. Palaskas, Y. Tsividis, „Dynamic Range Optimization of Weakly Nonlinear, Fully Balanced, Gm-C Filters with Power Dissipation Constraints”, IEEE Trans. Circuits Syst.-II, Vol.50, No.10, pp.714-727, Oct.2003.

[11] S. Koziel, S. Szczepanski, R. Schaumann, „General Approach to Continuous-Time Gm-C Filters”, Int. J. Circuit Theory Appl., Vol. 31, pp. 361-383, July/Aug. 2003.