Systematic stability-analysis method for analog circuits

ABSTRACT

Analyzing the stability of an analog circuit is an important part of the circuit design. Several commercial simulators are equipped with special stability analysis techniques. Problems arise when your design kit does not support such simulator. Another issue is when the designer wants to get insight into the sources of the instability to propose a stabilization. This can be done through analyzing the open-loop or the closed-loop transfer function of the circuit.The aim of this paper is to propose an automated analysis method which identifies the nodes to be considered for stabilization. The method does not need to break feedback loops or to manipulate netlists. It only uses AC simulations and does not require the full modified nodal equations. The method is illustrated on 3 design examples: a Voltage Controlled Oscillator (VCO), a reference bias circuit and the common-mode feedback network in a gm-C filter.

REFERENCES

• 1: B. Anderson and S. Vongpanitlerd. Network Analysis and Synthesis. Prentice-Hall, Eaglewood Cliffs, New Jersey, 1973.
• 2: P. Bolcato, J. Nallatamby, C. Rumolo, R. Larcheveque, and M. P. J. Obregon. Efficient algorithm for steady-state stability analysis of large analog/rf circuits. 1:451--454, May 2001.
• 3: G. Forsythe. Generation and use of orthogonal polynomials for data fitting with a digital computer. J. Soc. Indust. Appl. Math., 5:74--88, 1957.
• 4: Paul R. Gray , Robert G. Meyer, Analysis and Design of Analog Integrated Circuits, John Wiley & Sons, Inc., New York, NY, 1990
• 5: Jaime E. Kardontchik, Introduction to the design of transconductor-capacitator filters, Kluwer Academic Publishers, Norwell, MA, 1992
• 6: I. Kollar. Frequency Domain System Identification Toolbox V3.3 for Matlab. Gamax Ltd, Budapest, 2005.
• 7: Kenneth S. Kundert , Paul Gray, The Designer's Guide to Spice and Spectre, Kluwer Academic Publishers, Norwell, MA, 1995
• 8: R. Middlebrook. Measurement of loop gain in feedback systems. Int. J. Electronics, 38(4), 1975.
• 9: M. Milev and R. Butt. A tool and methodology for acstability analysis of continuous-time closed-loop systems. 3:204--208, March 2005.
• 10: S. Mons, J. Nallatamby, R. Quere, P. Savary, and J. Obregon. A unified approach for the linear and nonlinear stability analysis of microwave circuits using commercially available tools. IEEE Trans. Microwave Theory Tech., 47(12):2403--2409, Dec. 1999.
• 11: R. Pintelon and J. Schoukens. System Identification: A Frequency Domain Approach. IEEE Press, Inc. New York, 2001.
• 12: Y. Rolain and R. Pintelon. Generating robust starting values for frequency domain transfer function estimation. IEEE Trans. Automatic Control, 35(5):965--872, May 1999.
• 13: Y. Rolain, R. Pintelon, K. Xu, and H. Vold. Best conditioned parametric identification of transfer function models in the frequency domain. IEEE Trans. Automatic Control, 40(11):1954--1960, Nov. 1995.
• 14: Y. Rolain, J. Schoukens, and R. Pintelon. Order estimation for linear time-invariant systems using frequency domain identification methods. IEEE Trans. Automatic Control, 42(10):1408--1417, Oct. 1997.
• 15: W. Struble and A. Platzker. A rigorous yet simple method for determining stability of linear n-port networks. Gallium Arsenide Integrated Circuit (GaAs IC) Symposium, 1993, pages 251--254, Oct. 1993.
• 16: George D. Vendelin , Anthony M. Pavio , Ulrich L. Rohde, Microwave Circuit Design Using Linear and Nonlinear Techniques, Wiley-IEEE Press, 2005