Robust High-Gain Amplifier Design Using Dynamical Systems and Bifurcation Theory With Digital Postprocessing Techniques

A CMOS differential positive feedback amplifier (PFA) and its inherent nonlinearity were analyzed. Based on nonlinear dynamical systems and bifurcation theory, we predicted bifurcation and hysteresis phenomena in the PFA. An algorithm, which can be implemented using simple digital logic, was developed to measure the PFA´s open-loop stability as the bifurcation parameter changes. Parameter-tuning algorithms were constructed that systematically move the amplifier´s operational point towards the bifurcation point, at which an infinite dc gain is achieved. In order to compensate for the PFA´s high sensitivity to process and temperature variations, flexible analog design integrating digital programmability and adaptive digital postprocessing techniques were developed. This flexibility and postprocessing capability could dramatically enhance the PFA´s yield. Full corner simulation results over wide temperature range verified the bifurcation phenomena and the effectiveness of the control algorithms. It is shown that this amplifier can maintain high performance in advanced digital CMOS technology at very low voltage supply. It is also demonstrated that the proposed approach offers a robust PFA design with both high yield and high performance