a) and shows how electronic oscillator analysis can be made to fit within the same picture. The steps are illustrated for a harmonic oscillator. In a harmonic oscillator, the principle of oscillation relies on the exchange of energy between an inductive and a capacitive element. Here, the core system corresponds to a lossless resonant tank. Feedback transistors and tank losses are considered perturbation terms. The unperturbed (lossless) resonant tank is solved by a double-infinite set of steady-state oscillations. Each oscillation corresponds to a state of the core system and is identified by a value for its amplitude and starting phase. The perturbation terms, i.e. the currents coming from the feedback transistors and the tank losses, slowly drive the resonant tank from one state to another. Hence, they cause the tank's amplitude and phase to change with time. Averaging helps us to extract the equations that govern the slow-varying components of these changes. These components are the only ones that can grow large. 5.1.6 Modeling oscillator behavior The discussion above may have left the reader wondering what all of this has to do with the (behavioral) modeling of an oscillator's dynamic behavior. As stated before, system modeling starts with a thorough understanding of the system's behavior. Next, this understanding must be formalized by means of a mathematical model. As far as an oscillator's dynamic behavior is concerned, the equations that model the averaged state-changing behavior of the oscillator's core system turn out to provide an excellent starting point for the creation of compact behavioral models. These averaged equations capture the most essential part of an oscillator's dynamics. For the behavior of the earth, this involves the long-term changes in the position and shape of the earth's orbit around the sun. For a harmonic oscillator, this involves changes in amplitude and phase. Efficient behavioral modeling of oscillator dynamics can, therefore, be accomplished by means of suitable approximation