Chaotic Operation of a Colpitts Oscillator in the Presence of Parasitic Capacitances

A detailed description and analysis on the behaviour of a bipolar junction transistor in chaotic operation is presented. Bipolar Junction Transistors (BJTs) are basic ingredients of chaotic Colpitts oscillators, which aim at generating chaotic signals for secure communications. The high frequency operation of the chaotic oscillators is a challenging issue due to the parasitic capacitance of the junctions of a BJT. The presented analysis shows that the parasitic capacitances have adverse effects on the oscillator’s operation. They may generate conditions for chaotic oscillations or destroy them as well. Simulation results show that in order to determine more accurately the chaotic spectral signature and the performance of the system, the impact of the parasitic capacitances need to be taken into account during the design and analysis phase of the system. Key-words: Chaos, Colpitts Oscillator, Parasitic Capacitances, Bipolar Transistor.