In this paper, chaotic behavior of the Colpitts oscillator is studied and analyzed. The analyses consider the locally unstable behavior based on the linearization around the equilibrium and the globally bounded stability, which guarantees that the trajectories converge to an attractive and bounded set. The attractive set for the Colpitts oscillator is determined and characterized using Lyapunov analyses and an appropriate quadratic Lyapunov function. The theoretical results are accompanied by a representative simulation.