A multiple functional equivalence digital communications interface and a group of functional circuits are disclosed. The multiple functional equivalence digital communications interface presents a functional equivalence of each of a group of digital communications interfaces to a digital communications bus. Each functional equivalence of the group of digital communications interfaces is associated with a corresponding one of the group of functional circuits.

A circuit for amplifying a source signal generated by a signal source having a first impedance includes a transmission line transformer (TLT) having a first, a second, a third, and a fourth port wherein the TLT is coupled to receive the source signal at the first port and configured to output a corresponding impedance matched signal at the second port, the second port is coupled to the third port of the TLT, the circuit also including a TLT load having a first terminal coupled to the fourth port of the TLT and a second terminal coupled to a reference potential. The circuit additionally includes an amplifier device responsive to the impedance matched signal to generate an amplified signal.

A power amplifier circuit includes a first amplifier circuit configured to amplify a first signal of a first frequency band and output a first amplified signal having a first power, a second amplifier circuit configured to amplify a second signal of the first frequency band or a second frequency band different from the first frequency band and output a second amplified signal having a second power different from the first power, and a first variable adjustment circuit disposed between the second amplifier circuit and a first circuit subsequent to the second amplifier circuit, the first variable adjustment circuit being configured to be capable of adjusting a first impedance of the first circuit seen from the second amplifier circuit.

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.

A power amplifier module includes a first amplifier that amplifies an input signal to generate a first amplified signal and outputs the first amplified signal, a second amplifier that amplifies the first amplified signal to generate a second amplified signal and outputs the second amplified signal, and a matching network disposed between an output terminal of the first amplifier and an input terminal of the second amplifier. The first amplifier is provided on a first chip, and the second amplifier is provided on a second chip. The matching network has an impedance transformation characteristic adjustable in accordance with a control signal.

An active bias circuit for a power amplifier and a mobile terminal are disclosed. The circuit includes a proportional to absolute temperature (PTAT) current source circuit, a reference voltage circuit, an isolation voltage stabilizing circuit, and a bias voltage circuit. An input end of the PTAT current source circuit is connected to a voltage source (Vbat), and an output end is connected to the reference voltage circuit. The reference voltage circuit generates a reference voltage that is in proportion to a current and a temperature. The isolation voltage stabilizing circuit isolates the reference voltage circuit from the bias voltage circuit, and supplies a stabilized voltage to the bias voltage circuit by using a negative feedback loop. The bias voltage circuit receives the voltage of the isolation voltage stabilizing circuit, and is also connected to the voltage source (Vbat).

A power amplifier circuit includes a first amplifier transistor and a bias circuit. The first amplifier transistor amplifies a first signal and outputs a second signal. The bias circuit supplies a bias voltage or a bias current to the first amplifier transistor. The first amplifier transistor includes plural unit transistors disposed in a substantially rectangular region. The bias circuit includes first and second bias transistors and first and second voltage supply circuits. The first and second bias transistors respectively supply first and second bias voltages or first and second bias currents to the bases of unit transistors of first and second groups. The first and second voltage supply circuits respectively supply first and second voltages to the bases of the first and second bias transistors. The first and second voltages are decreased in accordance with a temperature increase. The second voltage supply circuit is disposed within the substantially rectangular region.

The disclosed technology includes device, systems, techniques, and methods for amplifying a complex modulated signal with a mixed-signal power amplifier. A mixed-signal power amplifier may include an input network for splitting an input signal to multiple signals with corresponding phase and amplitude offsets, a main power amplification path including at least an analog power amplifier for amplifying a first signal, one or more auxiliary power amplification paths including at least one digitally controlled analog power amplifier in each path for amplifying a second signal, and an output network for combining the two amplified signals. The main power amplification path and the auxiliary power amplification paths can operate together to achieve load modulation to enhance the overall power amplifier efficiency at power back-off mode and the overall power amplifier linearity. The disclosed technology further includes transmission systems incorporating the mixed-signal power amplifier.

A power amplification module includes a first input terminal arranged to receive a first transmission signal in a first frequency band, a second input terminal arranged to receive a second transmission signal in a second frequency band higher than the first frequency band, a first amplification circuit that amplifies the first transmission signal, a second amplification circuit that amplifies the second transmission signal, a first filter circuit located between the first input terminal and the first amplification circuit, and a second filter circuit located between the second input terminal and the second amplification circuit. The first filter circuit is a low-pass filter that allows the first frequency band to pass therethrough and that attenuates a harmonic of the first transmission signal and the second transmission signal. The second filter circuit is a high-pass filter that allows the second frequency band to pass therethrough and that attenuates the first transmission signal.

The present disclosure describes a method and system for linearizing an amplifier using transistor-level dynamic feedback. The method and system enables nonlinear amplifiers to exhibit linear performance using one or more of gain control elements and phase shifters in the feedback path. The disclosed method and system may also allow an amplifier to act as a pre-distorter or a frequency/gain programmable amplifier.