A receiver circuit is disclosed. The receiver circuit includes an amplifier configured to generate an RF signal based on a received signal, where the RF signal includes an information signal and a blocker signal modulating an RF carrier frequency. The receiver circuit also includes an RF filter connected to the amplifier, where the RF filter is configured to selectively attenuate the blocker signal.

In accordance with an embodiment, a method of operating an RF system includes filtering a wideband RF signal using an adjustable center frequency bandpass filter to produce a filtered RF signal; amplifying the filtered RF signal to produce an amplified RF signal; and band stop filtering the amplified RF signal to produce a band stopped RF signal.

A power amplifier includes a signal input unit to which an input signal is applied, an output stage that is electrically isolated from the signal input unit, where the output stage is configured to amplify an output signal of the signal input unit based on a power supply voltage from a floating power supply, a reference potential switch that is inserted between a reference node of the power supply voltage generated by the floating power supply and a reference potential line, and a feedback circuit configured to amplify a differential voltage between an output node of the output stage and the reference node, and feed the resultant voltage back to the signal input unit.

Amplifiers for radio-frequency applications. In some embodiments, a power amplifier die can include a semiconductor substrate and a plurality of narrow band power amplifiers implemented on the semiconductor substrate. Each narrow band power amplifier can be configured to operate with a high voltage in an average power tracking mode and be capable of being coupled to an output filter associated with a respective individual frequency band. Each narrow band power amplifier can be sized smaller than a wide band power amplifier configured to operate with more than one of the frequency bands associated with the plurality of narrow band power amplifiers.

An amplification apparatus as the embodiment of the present invention includes a switching amplifier and an adjuster. The switching amplifier is driven on the basis of a control signal and amplifies an input signal to be amplified to generate an amplified signal. The adjuster adjusts the control signal before it is inputted into the switching amplifier. Specifically, the adjuster adjusts at least one of a pulse width of the control signal and a delay time of the control signal with respect to the signal to be amplified.

Power amplifiers having reduced loss. In some embodiments, a power amplification system can include a plurality of power amplifiers, with each power amplifier being configured to receive and amplify a signal in a frequency band. The power amplification system can further include an output filter coupled to each of the power amplifiers by a separate output path such that the power amplification system is substantially free of a band selection switch between the plurality of power amplifiers and their corresponding output filters. Each power amplifier can be further configured to operate with a high-voltage supply to provide an impedance similar to an impedance of the corresponding output filter.

A gradient amplifier driver stage circuit includes: a gradient coil and a plurality of gradient driver modules electrically cascaded with each other and forming an output end, the output end being electrically connected to the gradient coil, wherein each gradient driver module includes a pre-stage power supply and a bridge amplifier connected in parallel, output voltage of the pre-stage power supplies of the plurality of gradient driver modules are the same, and each gradient driver module is configured to provide an inductive voltage drop and a resistive voltage drop on the gradient coil.

Doherty power amplifier having high supply voltage. In some embodiments, a power amplification system can include a supply system configured to provide a high-voltage supply signal, and a Doherty power amplifier having an input splitter configured to receive and split a signal into a carrier amplifier and a peaking amplifier. The Doherty power amplifier can further include a combiner configured to combine amplified signals from the carrier and peaking amplifiers to provide an output signal. The Doherty power amplifier can be configured to receive the high-voltage supply signal for operation of the carrier and peaking amplifiers. The power amplification system can further include an output path configured to couple the combiner to a filter. The Doherty power amplifier can have an impedance substantially the same as an impedance of the filter when operated with the high-voltage supply signal.

A multi-band power amplifier module includes at least one transmission input terminal, at least one power amplifier circuit that receives a first transmission signal and a second transmission signal through the at least one transmission input terminal, a first filter circuit that allows the first transmission signal to pass therethrough, a second filter circuit that allows the second transmission signal to pass therethrough, at least one transmission output terminal through which the first and second transmission signals output from the first and second filter circuits are output, a transmission output switch that outputs each of the first and second transmission signals output from the at least one power amplifier circuit to the first filter circuit or the second filter circuit, and a first tuning circuit that adjusts impedance matching between the at least one power amplifier circuit and the at least one transmission output terminal.

An apparatus has advanced amplifier Classes and low pass filter technologies for using software generated ascending or level waveforms that are effective when applying cardiac defibrillation and cardioversion waveforms which significantly reduce damage to the heart muscle. The apparatus comprises a waveform energy control system for delivering software generated waveforms comprising differentially driven Class D and Class B amplifier sections, wherein the Class D amplifier section produces Phase 1 ascending waveforms and has a programmable lowpass filter (LPF) and wherein the Class B amplifier section delivers hard-switched Phase 2 waveforms.