Optimale Systeme in der Mikroelektronik — Stabilität von Oszillatorschaltungen

An important topic in modern circuit design is the development of mixed analogue-digital circuits. Analogue circuits usually contain oscillating elements. Self-excited oscillating circuits transfer a constant input signal into an oscillating periodic output signal. The frequency is determined by the basic electronic elements, which are affected by production tolerances. In stability analysis the effects of these production tolerances are investigated, because they can cause a loss of stability, i. e. a bifurcation behaviour. Bifurcation is one of the main reasons for the birth of an irregular behaviour of a system. The implementation of a tool for stability analysis in a simulation package usually requires a charge-oriented approach for the investigation of local stability. For the investigation of industrial relevant circuits using a commercial simulator, it is necessary to adapt that approach to differential-algebraic equations. By means of perturbation technique, the monodromy matrix is computed. Its dominant eigenvalues help to characterize the reliability of the electronic circuit. The presented approach can be applied to network formulations in the time domain and in the frequency domain. In perspective, this approach can open the way to complete existing nonlinear CAD packages by a tool for automatic stability analysis.