A two-stage negative resistance enhancement model is presented based on research, theoretical derivation and analysis of Cascode oscillator. This general negative resistance model can be broadly used in chaotic circuit design. In practical circuit design, the negative resistance can be enhanced by replacing the lower-stage with an appropriate negative resistance unit. Simulation results show that the chaotic fundamental frequency f0 of the novel circuit is 4.2 GHz and the f0/fT value is up to 0.46, which is much higher than that of classical single-stage circuit.