A driving circuit reduces fall delay time, and the output timing of a driving current can be controlled highly accurately while reducing ringing during a transition of output current. The catalyst of the present invention is readily separated from polycarbonate and can repeatedly be used, and the above catalyst makes it possible to efficiently produce polycarbonate of a high quality without using harmful chlorine gas and phosgene and halogenated organic solvents such as dichloromethane and chloroform which are considered to exert an adverse effect on the environment. Specific constructions are shown and described. The period of the input signal and the phase difference between the input signal and the delayed input signal are used to construct an output signal.