A hybrid filter circuit for reducing common-mode interference signals with frequencies of at least 150 kHz in a power line with at least one phase. The circuit has a passive filter stage and an active filter unit with an active filter stage. The circuit can be coupled to an electrical device on a load side and to a power supply system on a supply side via the power line. The first active filter stage includes a sensor for measuring a common mode noise signal in the power line and a feedback unit with an active amplifier unit for generating a compensation signal counteracting the common mode noise signal, which is coupled into the power line via an output of the first active filter stage. The passive filter stage and the active filter circuit are arranged in cascade between the load terminal and a supply terminal.

A circuit comprising: a passive reactive component; and an active circuit, the active circuit arranged to increase the ac voltage difference across the reactive component by changing the current at an input to the reactive component and the current at an output of the reactive component by equal and opposite amounts. By increasing the current on one side of the resonant circuit and decreasing the current on the other side of the resonant circuit, the amount of current flowing through the resonant circuit is increased and thus the ac voltage difference across the inductor of the LC resonant circuit is increased. The Q of an inductor (the ratio of its imaginary to real impedance) is increased. In a filter, the improved Q provides a sharp, high rejection notch and faster pass-band to stop-band roll-off, thus improving the frequency response of the circuit.

A low noise amplifier includes at least two variable gain amplifier stages, each variable gain amplifier configured to accept an input signal and to provide a load driving signal; a tunable bandpass filter connected as a load to each variable gain amplifier stage, wherein each bandpass filter includes a resonant tank, each resonant tank including an inductor, wherein each inductor of each resonant tank is oriented in orthogonal relation with respect to each respective longitudinal axis of each next inductor, the orthogonal relation of the respective longitudinal axes configured to reduce mutual coupling between the tunable bandpass filters; a cross-coupled transistor pair, and at least one cross-coupled compensation transistor pair biased in a subthreshold region configured to add a transconductance component as a function of a load driving signal; and, a controller circuit configured to tune each tunable bandpass filter.

A low noise amplifier includes at least two variable gain amplifier stages, each variable gain amplifier configured to accept an input signal and to provide a load driving signal; a tunable bandpass filter connected as a load to each variable gain amplifier stage, wherein each bandpass filter includes a resonant tank, each resonant tank including an inductor, wherein each inductor of each resonant tank is oriented in orthogonal relation with respect to each respective longitudinal axis of each next inductor, the orthogonal relation of the respective longitudinal axes configured to reduce mutual coupling between the tunable bandpass filters; a cross-coupled transistor pair, and at least one cross-coupled compensation transistor pair biased in a subthreshold region configured to add a transconductance component as a function of a load driving signal; and, a controller circuit configured to tune each tunable bandpass filter.

An apparatus comprises a first RF port, a second RF port, a first resonator circuit and at least one second resonator circuit. The first resonator circuit and the second resonator circuit may be connected between the first RF port and the second RF port. The first resonator circuit may comprise a first inductor, a first capacitor, and a first stacked switch device. The second resonator circuit may comprise a second inductor, a second capacitor, and a second stacked switch device. The first capacitor and the first stacked switch device may be coupled in series across the first inductor. The second capacitor, the second inductor, and the second stacked switch device may be connected in parallel.

An apparatus comprises a first RF port, a second RF port, a first resonator circuit and at least one second resonator circuit. The first resonator circuit and the second resonator circuit may be connected between the first RF port and the second RF port. The first resonator circuit may comprise a first inductor, a first capacitor, and a first stacked switch device. The second resonator circuit may comprise a second inductor, a second capacitor, and a second stacked switch device. The first capacitor and the first stacked switch device may be coupled in series across the first inductor. The second capacitor, the second inductor, and the second stacked switch device may be connected in parallel.

An apparatus comprises a first series switch, a second series switch, a first shunt switch, a second shunt switch, a first DC blocking capacitor, and a second DC blocking capacitor. The first series switch may be coupled between a first RF port and a second RF port. The first shunt switch may be coupled between the first RF port and a first half supply voltage tab. The second series switch may be coupled between the second RF port and a third RF port. The second shunt switch may be coupled between the third RF port and a second half supply voltage tab. The first DC blocking capacitor may be coupled between the first half voltage tab and a circuit ground potential. The second DC blocking capacitor may be coupled between the second half supply voltage tab and the circuit ground potential.

An apparatus comprises a first series switch, a second series switch, a first shunt switch, a second shunt switch, a first DC blocking capacitor, and a second DC blocking capacitor. The first series switch may be coupled between a first RF port and a second RF port. The first shunt switch may be coupled between the first RF port and a first half supply voltage tab. The second series switch may be coupled between the second RF port and a third RF port. The second shunt switch may be coupled between the third RF port and a second half supply voltage tab. The first DC blocking capacitor may be coupled between the first half voltage tab and a circuit ground potential. The second DC blocking capacitor may be coupled between the second half supply voltage tab and the circuit ground potential.

A filter device includes a terminal, a switch that includes a common terminal and selection terminals and switches a connection of the common terminal to one of the selection terminals, a series arm resonator, and filter circuits. The filter circuits are connected to one end of the series arm resonator. The common terminal is connected to the terminal. One of the selection terminals is connected between one end of the series arm resonator and the filter circuits. Another one of the selection terminals is connected to the other end of the series arm resonator.

A filter device includes a terminal, a switch that includes a common terminal and selection terminals and switches a connection of the common terminal to one of the selection terminals, a series arm resonator, and filter circuits. The filter circuits are connected to one end of the series arm resonator. The common terminal is connected to the terminal. One of the selection terminals is connected between one end of the series arm resonator and the filter circuits. Another one of the selection terminals is connected to the other end of the series arm resonator.