Stability Characterizing Function for Electronic Circuit Design Based on Frequency-Domain Analysis With Parametric Damping

A stability characterizing function (SCF) to be used for small and large-signal stability analysis and design of single and multitransistor electronic circuits is proposed. Stability constraints based on this function can be integrated with the framework of standard computer-aided design (CAD) procedures. The method is based on the bounded-input–bounded-output (BIBO) stability criterion, where a suitable set of input and output variables is chosen at the ports of all the nonlinear intrinsic electron device (IED) models. These variables are linked by a nonlinear state perturbation (NSP) matrix, whose elements are directly computed by analyzing an associated parametrically damped (PD) (i.e., stabilized) circuit. The proposed SCF is defined in terms of the NSP matrix elements and is a scalar function of frequency and the damping parameter. Circuit stability margins are easily evaluated by visual inspection of the plot of this function. Preliminary experiment validation is carried out by applying this approach for checking the self-starting capabilities of an oscillator as well as for the small and large-signal stability analysis of a two-transistor balanced amplifier and a single-transistor PA.