Filter circuit arrangement

A filter circuit arrangement comprising an inductive element and an electronic reactance circuit, said electronic reactance circuit comprising an amplifier arrangement the input of which is connected across said inductive element and the output of which is coupled to said inductive element, characterised in that said inductive element is constituted by a first port of a gyrator circuit the second port of which is capacitively loaded, in that said amplifier arrangement, is a voltage amplifier arrangement, the output circuit of which is connected effectively in series with an input signal path through said inductive element in such manner that said output circuit is external to the circuit loop which includes the reactive element and the input circuit of the voltage amplifier, in that a capacitive element is included in series in said input signal path, in that first means are provided for presenting an input signal path, in that first means are provided for presenting an input signal voltage across the effective series arrangement of the inductive element, the capacitive element and said output circuit, in that second means are provided for deriving an output signal voltage from across a part of said series arrangement which includes said capacitive element and said inductive element, and in that said output circuit is connected in said series arrangement in such a sense that, within this series arrangement, the signal voltage produced across said output circuit by the voltage amplifier when said input signal voltage is present will be in phase with the signal voltage occurring across said inductive element.