A power amplifier (100, 200, 500, 800, 1100) for amplifying an input signal into an output signal is disclosed. The power amplifier (100, 200, 500, 800, 1100) comprises an input port (110) for receiving the input signal and an output port (130) coupled to an output transmission line (140) for providing the output signal. The power amplifier (100, 200, 500, 800, 1100) further comprises multiple sets of sub-amplifiers (150, 160, 170, 180) distributed along the output transmission line, and inputs of the subamplifiers are coupled to the input port, outputs of the sub-amplifiers are coupled to the output transmission line. At least two different supply voltages are provided for the sub-amplifiers in the multiple sets of sub-amplifiers (150, 160, 170, 180).

A power amplifier has a number n of power cells A.sub.i, a number n of output transmission lines TL.sub.1i for combining output powers from the power cells, and a number n of impedance transformation network ITN.sub.i, where i=1, . . . n. The number n of output transmission lines are connected in series. The output terminal of each power cells is connected to its output transmission line via its impedance transformation network. Each impedance transformation network is an upward impedance transformation network for transforming an output impedance of each power cell at the input terminal of the impedance transformation network into a higher impedance at the output terminal of the impedance transformation network. A number n of input transmission lines TL.sub.0i (i=1, 2 . . . n)=connected in series. The input terminal of the i-th power cell is connected to the second terminal of the i-th transmission line via a capacitor, where i=1, . . . n.

A distributed amplifier includes an input transmission circuit, an output transmission circuit, at least one cascode amplifier coupled between said input and output transmission circuits. Each cascode amplifier includes a first common-gate configured transistor coupled to the output transmission circuit, a common-source configured transistor coupled between the input transmission circuit and the common-gate configured transistor, and a second common-gate configured transistor coupled between the first common-gate configured transistor and common-source configured transistor.

An inverted three-stage Doherty amplifier is disclosed. The amplifier provides an input power divider, a carrier amplifier, two peak amplifiers, and an output combiner. The output combiner includes five quarter-wavelength (/4) lines, three of which correspond to three amplifiers, one of rest two /4 lines combines an output of the carrier amplifier with an output of the first peak amplifier, the last /4 line combines the combined output of the carrier amplifier and the first peak amplifier with an output of the second peak amplifier. The five /4 lines have respective impedance to optionally adjust output impedance of the respective amplifiers.

An apparatus includes an input transformer, an amplifier and an output transformer. The input transformer may be on a substrate and configured to convert an input signal into a differential input signal. The input signal may be a radio-frequency signal. The amplifier may be on the substrate and configured to generate a differential output signal in response to the differential input signal. The amplifier may be a balanced and distributed amplifier. The output transformer may be on the substrate and configured to convert the differential output signal into an output signal. Each of the input transformer and the output transformer may be a three line coupled balun transformer with a variable bandpass bandwidth.

A distributed amplification device with p inputs, p outputs, p amplification paths comprises a redundant reservoir of n amplifiers including n-p back-up amplifiers, an input redundancy ring and an output redundancy ring formed by rotary switches, the input and output redundancy rings sharing the same technology. The internal amplification pathways associated with the n-p back-up amplifiers frame in an interlaced manner the internal amplification pathways associated with the p nominal amplifiers and the amplification paths of the routing configurations each pass through at least five rotary switches. The input and output redundancy rings are topologically and geometrically configured and the family of the routing configurations is chosen such that the electrical lengths of all the paths of one and the same routing configuration of the family are equal.

A new method for amplifying signals having higher bandwidth, lower T.H.D, higher efficiency, smaller circuit size and lower costs in design, has been developed. A clipped signal is amplified to smaller pieces and each smaller part is amplified. Adding clipped amplified signals to each other, the main amplified signal is generated.

A technique relates to a qubit readout system. A cavity-qubit system has a qubit and a readout resonator and outputs a readout signal. A lossless superconducting circulator is configured to receive the microwave readout signal from the cavity-qubit system and transmit the microwave readout signal according to a rotation. A quantum limited directional amplifier amplifies the readout signal. A directional coupler is connected to and biases the amplifier to set a working point. A microwave bandpass filter transmits in a microwave frequency band by passing the readout signal while blocking electromagnetic radiation outside of the microwave frequency band. A low-loss infrared filter has a distributed Bragg reflector integrated into a transmission line. The low-loss filter is configured to block infrared electromagnetic radiation while passing the microwave readout signal. The low-loss infrared filter is connected to the microwave bandpass filter to receive input of the microwave readout signal.

A technique relates to a qubit readout system. A cavity-qubit system has a qubit and a readout resonator and outputs a readout signal. A lossless superconducting circulator is configured to receive the microwave readout signal from the cavity-qubit system and transmit the microwave readout signal according to a rotation. A quantum limited directional amplifier amplifies the readout signal. A directional coupler is connected to and biases the amplifier to set a working point. A microwave bandpass filter transmits in a microwave frequency band by passing the readout signal while blocking electromagnetic radiation outside of the microwave frequency band. A low-loss infrared filter has a distributed Bragg reflector integrated into a transmission line. The low-loss filter is configured to block infrared electromagnetic radiation while passing the microwave readout signal. The low-loss infrared filter is connected to the microwave bandpass filter to receive input of the microwave readout signal.

Methods and apparatuses for controlling impedance in intermediate nodes of a stacked FET amplifier are presented. According to one aspect, a series-connected resistive and capacitive network coupled to a gate of a cascode FET transistor of the amplifier provide control of a real part and an imaginary part of an impedance looking into a source of the transistor. According to another aspect, a second parallel-connected resistive and inductive network coupled to the first network provide further control of the real and imaginary parts of the impedance. According to another aspect, a combination of the first and/or the second networks provide control of the impedance to cancel a reactance component of the impedance. According to another aspect, such combination provides control of the real part for distribution of an RF voltage output by the amplifier across stacked FET transistors of the amplifier.