... Proceedings of 2001 Int. Symposium on Nonlinear Theory and its Applications, . Miyagi, Japan, October 28 - November 1, 2001 , vol. 1, pp. ... Chaotic oscillators based on RC-elements and nonlinear amplifiers with sigmoid function only are discussed. The analysis of the structure a number of well-known oscillators is carried out. On the basis of that analysis the structure of the oscillators which consist of RC–elements and op-amps only and capable to show chaotic oscillations is suggested. ...