CFA BASED UNIVERSAL BIQUAD FILTER

Maria Cristina Piccirilli,
Department of Electronics and Telecommunications, University of Florence, Firenze, Italy

DOI: 10.36724/2664-066X-2021-7-3-2-5

SYNCHROINFO JOURNAL. Volume 7, Number 3 (2021). P. 2-5.

Abstract

This paper is a review of the organizational structure and challenges that a technological enterprise faces during scaling, from the perspective of the engineering management. After expanding operations internationally, the distributed engineering teams developing hardware and software for internet of things applications, face issues regarding culture, communication, leadership, project planning and management. Relevant literature addressing these issues is presented. We elaborate on already implemented measures for improving the overall efficiency and propose further processes introduced in recent literature that can be beneficial for further optimizing the new product development. Potential knock-on effects by such implementation are also discussed. A universal biquad filter using current feedback amplifiers (CFA) as active devices and a canonical number of capacitors is presented. It realizes the classical feedforward structure through the use of grounded capacitors and MOS transistors, which permit a full integrability. The proposed circuit has attractive characteristics, as the possibility to electronically control the transfer function coefficients and the possibility to be directly inserted within cascaded configurations. The theoretical analysis of the circuit is followed by some PSPICE simulation results in agreement with the theoretical findings. In this paper a universal fully integrable biquad using CFAs as active devices and a canonical number of capacitors is presented. It realizes the classical feedforward structure [3] through the use of grounded capacitors and MOS transistors. The presence of grounded capacitors makes the proposed circuit absorb shunt parasitic capacitances. All the possible kinds of responses can be realized, while in the biquad reported in [2] only the low-pass and band-pass responses can be obtained. The numerator and denominator coefficients of the voltage transfer function of the proposed biquad can be electronically controlled by acting on the gate voltages of the MOS transistors of the circuit. Moreover the presented structure has a low-impedance output and then it can be cascaded without additional buffers.

Keywords: Analog circuits, continuous-time filters.

References

[1] S. Franco, “Design with operational amplifiers and analog integrated circuits”, McGraw-Hill, New York, 1998.
[2] M. C. Piccirilli, “A fully integrated Tow-Thomas biquad using current feedback amplifiers”, Proc. International Conference on Electronics, Circuits and Systems, Pafos, Cyprus, pp.1325-1328, 1999.
[3] G. Daryanani, “Principles of active network synthesis and design”, John Wiley, New York, 1976.
[4] S. Takagi, Z. Czarnul, T. Iida, N. Fujii, “Generalization of MRC circuits and its applications”, IEEE Trans. on Circuits and Systems-I, Vol. 44, No. 9, pp. 777-784, 1997.
[5] N. I. Khachab, M. Ismail, “MOS multiplier/divider cell for analogue VLSI”, Electronics Letters, Vol. 25, No. 23, pp. 1550-1552, 1989.