Recently have been reported methods to deliver a digital filter from an analog active filter, described only by its circuits diagram. The proposed approaches have been implemented in MATLAB and Python, and they were based on state-space conversion from analog to digital domain. Based on the Python approach, we show in this paper how to compute the transfer function of a large order analog active filter. The analog filter is described only by its circuits diagram. Finally, the analog filter is converted to the corresponding digital filter, having similar frequency gain and phase characteristics.
If the inline PDF is not rendering correctly, you can download the PDF file here.
 J. Vlach and K. Singhal Computer Methods for Circuit Analysis and Design 2nd ed. New York NY USA: John Wiley & Sons Inc. 1993.
 L. D. Chua and P.-M. Lin Computer-Aided Analysis of Electronic Circuits. Englewood Cliffs NJ: Prentice Hall 1975.
 C. Rusu L. Grama and J. Takala “SPICE simulation of analog filters: A method for designing digital filters” in Proceedings EUROCAST 2009 Gran Canaria Feb. 2009 pp. 179–180.
 L. Grama A. Lodin C. Rusu and J. Takala “Method to convert analog filters to digital filters” in Proceedings ISPA 2013 Sep. 2013 pp. 451–456.
 A. Lodin L. Grama C. Rusu and J. Takala “Systematic method to convert of analog filters to digital filters” in Proceedings of 2013 IEEE Workshop on Signal Processing Systems 2013 pp. 189–194.
 A. Lodin L. Grama and C. Rusu “From bulky analog active filters to digital filters” in Proceedings of the International Symposium on Electronics and Telecommunications 2018 - ISETC 2018 2018 pp. 1–4.
 N. Balabanian and T. A. Bickart Electrical Network Theory. New York: John Willey & Sons 1969.
 L. Grama A. Lodin and C. Rusu “About converting active analog filters to digital filters” Acta Technica Napocensis - Electronics and Telecommunications vol. 57 no. 4 pp. 36–39 2016.
 M. Silisteanu L. Cipere and C. Constantinescu Lucrari practice de depanare a receptoarelor de televiziune. Bucuresti: Editura Didactica si Pedagogica Bucuresti 1982.