A notch filter including an inductor-capacitor tuning circuit is disclosed. The inductor-capacitor tuning circuit may determine a frequency response of the notch filter in accordance with an associated resonant frequency. In some exemplary embodiments, the inductor-capacitor circuit may include a differential inductor divided at a symmetry point and a variable capacitor coupled to the differential inductor at the symmetry point.

A notch filter including an inductor-capacitor tuning circuit is disclosed. The inductor-capacitor tuning circuit may determine a frequency response of the notch filter in accordance with an associated resonant frequency. In some exemplary embodiments, the inductor-capacitor circuit may include a differential inductor divided at a symmetry point and a variable capacitor coupled to the differential inductor at the symmetry point.

A power amplifier includes: a transistor having a gate electrode, a source electrode and a drain electrode; a passive component part connected to the gate electrode through a gate wiring; and a harmonic circuit connected between the source electrode and the gate wiring and disposed in a region between the gate electrode and the passive component part and between the source electrode and the gate wiring.

The present invention provides an apparatus and a method for amplifying a radio-frequency signal and an MRI system comprising the apparatus. An aspect of the present invention proposes an apparatus for amplifying a radio-frequency (RF) signal comprising: a magnetically insensitive input balun (10) for converting the RF signal in unbalanced format into balanced signals; at least two groups of MOSFETs, each group including at least one MOSFET (30, 40), for respectively amplifying the balanced signals in a push-pull way; a magnetically insensitive output balun (60) for converting the amplified balanced signals into an unbalanced format; a magnetically insensitive input matching network (20, 20) for matching input impedances of the at least two groups of MOSFETs with output impedances of the magnetically insensitive input balun (10); a magnetically insensitive output matching network (50, 50) for matching output impedances of the at least two groups of MOSFETs with input impedances of the magnetically insensitive output balun (60); a magnetically insensitive protection circuit (70, 70) for protecting a direct current (DC) power supply which provides DC for driving the at least two groups of MOSFETs from the amplified balanced signals. The proposed apparatus not only has a high power output but is also magnetically insensitive, so that it can operate in an environment of strong magnetic fields, such as the MRI scanner room.

Systems, devices and methods related to multi-band power amplifier. In some embodiments, a power amplifier module includes a power amplifier having an output stage and configured to receive a signal. The power amplifier module also includes a first programmable harmonic termination circuit in electrical communication with the output stage of the power amplifier. The first programmable harmonic termination circuit includes a first plurality of capacitors and a first plurality of switches, with at least one of the first plurality of capacitors being in electrical communication with at least one of the first plurality of switches. The power amplifier module further includes a controller configured to modify a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on a second harmonic frequency of the signal.

Systems, devices and methods related to multi-band power amplifier. In some embodiments, a power amplifier module includes a power amplifier having an output stage and configured to receive a signal. The power amplifier module also includes a first programmable harmonic termination circuit in electrical communication with the output stage of the power amplifier. The first programmable harmonic termination circuit includes a first plurality of capacitors and a first plurality of switches, with at least one of the first plurality of capacitors being in electrical communication with at least one of the first plurality of switches. The power amplifier module further includes a controller configured to modify a configuration of the first plurality of switches of the first programmable harmonic termination circuit based at least in part on a second harmonic frequency of the signal.

Disclosed are systems and methods related to matching an impedance of the power amplifier to an impedance of the antenna in a power amplifier module that includes an amplifier circuit residing on a first semiconductor die and an output matching network (OMN) that includes a first partial OMN and a second partial OMN. The first partial OMN resides on the first semiconductor die and matches an output impedance of the amplifier circuit to an input impedance of the second partial OMN. The second partial OMN matches an output impedance of the first partial OMN with an input impedance of the antenna and is not part of the first semiconductor die.

Provided is a current output circuit that includes: a first FET that has a power supply voltage supplied to a source thereof, that has a first voltage supplied to a gate thereof and that outputs a first current from a drain thereof; a second FET that has the power supply voltage supplied to a source thereof, that has the first voltage supplied to a gate thereof and that outputs an output current from a drain thereof; a first control circuit that controls the first voltage such that the first current comes to be at a target level; and a second control circuit that performs control such that a drain voltage of the first FET and a drain voltage of the second FET are made equal to each other.

Provided is a current output circuit that includes: a first FET that has a power supply voltage supplied to a source thereof, that has a first voltage supplied to a gate thereof and that outputs a first current from a drain thereof; a second FET that has the power supply voltage supplied to a source thereof, that has the first voltage supplied to a gate thereof and that outputs an output current from a drain thereof; a first control circuit that controls the first voltage such that the first current comes to be at a target level; and a second control circuit that performs control such that a drain voltage of the first FET and a drain voltage of the second FET are made equal to each other.

A Doherty power amplifier includes a carrier amplifier, a peaking amplifier, and a peaking amplifier bias circuit coupled to the peaking amplifier and configured to provide a peaking amplifier bias signal to the peaking amplifier based on a saturation level of the carrier amplifier.