ACTIVE BAND-PASS FILTER Russian patent published in 2018 - IPC H03H7/12 

FIELD: electricity.

SUBSTANCE: filter contains a common bus, input and output potential terminals, an operational amplifier with two inputs connected to its inputs by the first outputs the first and the second two-terminal elements, the second outputs of which are connected to each other and by an inductance coil with an input potential terminal, and its output is connected to the output potential terminal. The first and second two-terminal elements are made in the form of a series-connected condenser and two-terminal element, made in the form of a parallel connected inductance coil and condenser. The first outputs of the first and the second rejective two-terminal elements are connected to the second outputs of the first and the second two-terminal elements, the second outputs of which are connected to the common bus, each rejective two-terminal element contains an inductance coil, an electronic key and a variable capacity condenser connected in series.

EFFECT: active band-pass filter circuit with returnable rejection.

1 dwg