The operational amplifier disclosed includes an input stage configured to receive power from a floating supply circuit in in a low voltage range that can float according to the common mode voltage at the input. The low voltage supply facilitates the use of low voltage components that can improve the precision of the operational amplifier by lowering the offset voltage. The input stage utilizes a first gain block and a second gain block. The first gain block is configured to have a low offset voltage while the second gain h block is configured to have a high gain. Dividing these aspects over separate gain blocks improves the precision and noise performance of the operational amplifier. The operational amplifier has high gain at low frequencies and at high frequencies due to a topology that combines a low gain, high bandwidth path with a high gain, low bandwidth path at the output.

A Doherty amplifier includes: a carrier amplifier that amplifies a first signal; a peak amplifier that amplifies a second signal; and a synthesis circuit that synthesizes the first signal amplified by the carrier amplifier and the second signal amplified by the peak amplifier, and the synthesis circuit includes a bandpass filter circuit that includes parasitic capacitances at respective output sides of the carrier amplifier and the peak amplifier as capacitors.

The present disclosure provides an audio system. The audio system includes: a target audio signal generator module including a plurality of target audio signal generators, configured to receive an audio signal and a tracking signal and generate a plurality of target audio signals based on the audio signal and tracking signal; a tracking power supply circuit module including a plurality of tracking power supply circuits, configured to receive the plurality of target audio signals and generate a plurality of power supply voltages based on the plurality of target audio signals; an audio power amplifying circuit module including a plurality of audio amplifying circuits, configured to receive the plurality of target audio signals and the plurality of power supply voltages, and amplify the plurality of target audio signals; wherein each of the plurality of tracking power supply circuits provides a corresponding power supply voltage for each of the plurality of audio amplifying circuits.

A power amplification system may include a shared common cascode input stage. A power amplification system may include a plurality of cascode output stages parallelly connected to the shared common cascode input stage, each cascode output stage associated with a frequency band.

A power amplifier includes a first amplifier configured to amplify an input signal and output, from a first output, a first signal in which the input signal is amplified, a second amplifier configured to amplify the first signal and output, from a second output, a second signal in which the first signal is amplified, a third amplifier configured to amplify the second signal and output, from a third output, a third signal in which the second signal is amplified, a capacitor connected between the first output and a mixing node, a first resistor connected between the second output and the mixing node, a first inductor connected between the third output and the mixing node, a second inductor connected between the mixing node and a load, and a feedback circuit configured to negatively feed back a mixed signal of the mixing node to an input of the first amplifier.

A bias circuit includes: a first transistor having an emitter or a source which supplies a bias to an amplifier operating by a power source voltage through a first resistive element and a base or a gate; a first capacitor having a first end electrically connected to the base or the gate of the first transistor and a second end connected to a ground; and a second transistor having a collector or a drain electrically connected to the base or the gate of the first transistor, a base or a gate electrically connected to the base or the gate of the first transistor, and an emitter or a source connected to a node which is supplied with a signal with experience of being amplified by the amplifier and the power source voltage.

The invention provides a differential power amplification stage comprising a first amplification unit adapted to amplify a first differential signal and to output an amplified first differential signal, a second amplification unit adapted to amplify a second differential signal having opposite phase to the first differential signal and to output an amplified second differential signal, and a saturation detection unit adapted to detect gain saturation of the first and second amplification unit, to generate a saturation detection signal indicating the gain saturation of first and second amplification unit, and to provide a virtual ground for the first and second differential signals for RF cancellation on the first and second differential signals. The virtual ground principle is also applied to a Doherty power amplifier module which comprises a saturation detection unit for detecting saturation in the carrier amplification stage.

An apparatus including an inner conductor and an outer conductor. The inner conductor may comprise a cylindrical portion, a tapered end and a plurality of blades. The blades may be arranged around the cylindrical portion and extend along a length of the cylindrical portion with a predetermined shape. The shape may have a probe at a first end and a second end of the shape may meet the cylindrical portion. The tapered end may have an input/output (I/O) transition. The outer conductor may comprise a cavity, a first connector and a plurality of second connectors. The inner conductor may be within the cavity. The first connector may be connected to the I/O transition. Each of the second connectors may be connected to the probe of one of the blades. The shape of each of the blades may be configured to provide a low-loss transition for a microwave signal.

Apparatus and methods for an improved-efficiency Doherty amplifier are described. The Doherty amplifier may include a two-stage peaking amplifier that transitions from an off state to an on state later and more rapidly than a single-stage peaking amplifier used in a conventional Doherty amplifier. The improved Doherty amplifier may operate at higher gain values than a conventional Doherty amplifier, with no appreciable reduction in signal bandwidth.

A Doherty amplifier includes: a carrier amplifier to amplify a first high frequency signal having a first higher harmonic and a second higher harmonic; a peak amplifier to amplify a second high frequency signal having the first higher harmonic and the second higher harmonic; a first series resonant circuit connected between an output end of the carrier amplifier and a ground, and configured to resonate at the frequency of the first higher harmonic; a second series resonant circuit connected between an output end of the peak amplifier and the ground, and configured to resonate at the frequency of the first higher harmonic; a first parallel resonant circuit configured to resonate at the frequency of the second higher harmonic; and a second parallel resonant circuit configured to resonate at the frequency of the second higher harmonic.