Abstract: A variable delay device includes a variable delay circuit (12) and a correction circuit (14). On the basis of output signals R and V from variable delay lines (30, 32) of the correction circuit, an output signal V.sub.L by which a control characteristic of a variable delay line (16) is made substantially linear is outputted to the variable delay circuit from a linearity detector (34) of the correction circuit. The output signals R and V are also applied to a variable range detector (36), and on the basis of an output of the detector (36), an output signal V.sub.r by which a variable range of the variable delay line (16) is made constant is outputted to the variable delay circuit (12) from a reference level generator (38) of the correction circuit. The output signal V.sub.L determines an input/output characteristic of a non-linear circuit (22) which is included in the variable delay circuit and modifies a variable amount control signal V.sub.d, and the output signal V.sub.

Abstract: An equivalent inductance circuit includes a feedback type integration circuit and a differential amplifying circuit. An input signal applied to an input terminal is integrated by the feed-back type integration circuit and, a signal according to a difference component between an integrated output signal and the input signal is outputted by the differential amplifying circuit. By feeding the difference signal back to the input terminal, an input impedance equivalently represents an inductance characteristic. Such equivalent inductance can be changed by a current from a variable current source which supplies the current to the differential amplifying circuit and, a change of the equivalent inductance shows an inverse proportional manner.