Colpitts and Chaos

Erik Lindberg
Department of Information Technology
343 Technical University of Denmark, DK-2800 Lyngby, DENMARK
E-MAIL:, FAX: +45 4593 0355

The chaotic behaviour of the Colpitts oscillator reported by M.P. Kennedy is further investigated by means of PSpice simula- tions. Chaos is also observed with the default Ebers-Moll BJT transport model with no memory. When the model is extended with memory and losses chaos do not occur and a 3'rd order limit cycle is found. If then the forward Early voltage parameter is added chaos is observed again. An examination of the eigenvalues of the oscillator with the simple memoryless Ebers-Moll BJT injec- tion model is presented. By adding bulk resistors to the model stable limit cycles of orders 1, 2, 3 and 4 are found.