“…For instance, the chaotic circuits that were early proposed based on a positive-feedback loop [4] and a biquadratic filter [5], a chaotic circuit based on a single opamp has employed a diode [6], whereas a chaotic jerk circuit based on two opamps has employed sgn(x) nonlinearity [7]. Recently, current-tunable chaotic circuits have been demonstrated for such a category using either exponential nonlinearity of a diode with a single opamp [8,9], or sgn(x) nonlinearity with two opamps [10].…”