RC Active Networks Using Current Inversion Type Negative Impedance Converters

The RC active filter, which has been established by J. G. Linvill, has a circuit configuration of a negative impedance converter sandwiched between two RC networks. This paper deals with a new circuit also using two RC networks and a converter, but its configuration is based on the parallel or series connection and the converter must be a current-inversion type. The main results obtained here are as follows: 1) The filter characteristic function which has attenuation poles at finite frequency can be realized by the synthesis of only RC two-terminal impedances without using twin- circuits. 2) The characteristic all-pass function is realized by the same method as a filter characteristic. 3) A current-inversion type converter, which uses a pair of unction transistors or vacuum tubes, is obtained. 4) Some design examples and experimental results are reported on filters and phase shifters.