Abstract  The excited source of non-autonomous circuit of first order is a non-sine periodic source. The shape and property of forced oscillation of first order circuits depend on the constitute of excited source. Itpossess universal law that the oscillation pattern vary with excited cycle. The variable law is identical for different dynamic elements. The long-short of forced oscillation cycle depend on the low-high of fundamental frequency of excited source. The oscillation cycle gradually extend, the pattern of phase portrait can progressively evolve to chaotic state from periodic state. The periodic state can obviously obtain a closed period orbit in the simulation interval, the closed orbit may be single circle or multi-circle. The phase portrait of chaotic state is much more complex than the periodic state, it cannot display the close of trajectory in the simulation interval finally, therefore it is considered as non-periodic chaos . The common characteristics of variable law of oscillation pattern are displayed by means of using two sort of example for different dynamic elements in this paper.

Key words  first order circuit; chaotic state; periodic state; forced oscillation; excited cycle