Three third-order differential equations are obtained for the canonical system. These equations are equivalent to the initial system and characterize its components. The first equation is Lipschitz continuous, the second one has discontinuous right hand side and the third one is an equation with impulse action. The equation in variations which corresponds to solutions of the first equation is investigated; analysis of its solutions is given; conditions for presence of periodic solutions for Chua’s system are discussed. The canonical form for the general system of Chua’s type is obtained.