Certain aspects of the present disclosure provide methods and apparatus for implementing an amplification system. The amplification system includes an amplifier comprising differential inputs and an output. The differential inputs include an inverting input and a non-inverting input. The amplification system further includes a feedback path from the output coupled to the inverting input. The feedback path from the output is coupled to at least one of an inverting amplifier or buffer, and the at least one of the inverting amplifier or buffer is further coupled to the non-inverting input.

An amplifier system having: an amplifier having a linear operating region where an output signal produced by the amplifier at the output terminal has a power level increasing proportionally with the increasing input signal power level up to a compression region of the amplifier where the output power is inhibited from increasing with increasing input signal power; and a DC current limiting circuit, coupled between a DC power supply and the amplifier, to: supply DC current from the DC power supply that is equal to quiescent current to the amplifier from the DC power supply when the amplifier operates in the linear region; enable the amplifier to draw increasing DC current from the DC power supply above the quiescent current with increasing input signal power until the output signal power reaches the desired compression point level which is lower than that of a stand-alone amplifier without the DC current limiting circuit; and, then limits the current drawn by the amplifier from the DC power supply.

An amplifier system having: an amplifier having a linear operating region where an output signal produced by the amplifier at the output terminal has a power level increasing proportionally with the increasing input signal power level up to a compression region of the amplifier where the output power is inhibited from increasing with increasing input signal power; and a DC current limiting circuit, coupled between a DC power supply and the amplifier, to: supply DC current from the DC power supply that is equal to quiescent current to the amplifier from the DC power supply when the amplifier operates in the linear region; enable the amplifier to draw increasing DC current from the DC power supply above the quiescent current with increasing input signal power until the output signal power reaches the desired compression point level which is lower than that of a stand-alone amplifier without the DC current limiting circuit; and, then limits the current drawn by the amplifier from the DC power supply.

A radio circuit, comprises an antenna; a differential power amplifier, comprising differential transmit inputs and differential transmit outputs, configured to amplify differential transmit signals received via the differential transmit inputs and output the amplified differential transmit signals via the differential transmit outputs; a differential low noise amplifier, comprising differential receive inputs and differential receive outputs, configured to receive differential receive signals via the differential receive inputs and output amplified differential receive signals via the differential receive outputs; and a transformer comprising a primary winding and a secondary winding, the primary winding coupled with the differential transmit outputs of the power amplifier and the differential receive inputs of the low noise amplifier and the secondary winding coupled with the antenna.

A power amplifier circuit includes a first transistor, a second transistor, a first bias circuit supplying a first bias current or voltage, a second bias circuit supplying a second bias current or voltage, a first inductor, and a first capacitor. A power supply voltage is supplied to a collector of the first transistor, and an emitter thereof is grounded. A radio frequency signal and the first bias current or voltage are supplied to a base of the first transistor. The power supply voltage is supplied to a collector of the second transistor, and an emitter thereof is connected to the collector of the first transistor via the first capacitor and is grounded via the first inductor. The second bias current or voltage is supplied to a base of the second transistor. An amplified radio frequency signal is output from the collector of the second transistor.

A power amplifier circuit includes a first transistor, a second transistor, a first bias circuit supplying a first bias current or voltage, a second bias circuit supplying a second bias current or voltage, a first inductor, and a first capacitor. A power supply voltage is supplied to a collector of the first transistor, and an emitter thereof is grounded. A radio frequency signal and the first bias current or voltage are supplied to a base of the first transistor. The power supply voltage is supplied to a collector of the second transistor, and an emitter thereof is connected to the collector of the first transistor via the first capacitor and is grounded via the first inductor. The second bias current or voltage is supplied to a base of the second transistor. An amplified radio frequency signal is output from the collector of the second transistor.

An amplifier system including a push-pull power amplifier having an input to receive a radio frequency (RF) input signal and an output, the push-pull power amplifier being configured to amplify the RF input signal and provide at the output an RF output signal that is an amplified version of the RF input signal, a switchable shunt capacitance switchably connected between a load-line connected to the output of the push-pull power amplifier and a reference potential, and a switch configured to selectively connect the switchable shunt capacitance to the reference potential and disconnect the switchable shunt capacitance from the reference potential to vary an impedance of load-line.

A semiconductor device includes: a semiconductor substrate whose contour is a pentagon; a front-stage amplifier formed relatively near a vertex of the pentagon of the semiconductor substrate; and a rear-stage amplifier formed relatively near a side opposed to the vertex of the semiconductor substrate and amplifying an output from the front-stage amplifier.

A millimetre (mm) wave power amplifier includes a plurality of amplifiers, each amplifier including an amplifying FET including a gate, drain and source. The mm wave power amplifier also includes an input port, an output port, a VDS port being connected to a VDS voltage source for setting the drain-source voltage of the FET, and a VGS port being connected to a VGS voltage source for setting the gate-source voltage of the FET. The output ports of the amplifiers are connected to a signal combiner and the input ports of the amplifiers are connected to a signal splitter. At least one of (a) at least two of the VGS ports are connected to different VGS voltage sources, and (b) at least two of the VDS ports are connected to different VDS voltage sources.

Cascode power amplifier bias circuits suitable for operating across multiple power supply domains are provided. In certain embodiments, a power amplifier system includes a cascode power amplifier and a multi-domain bias circuit that generates at least a first cascode bias voltage for the cascode power amplifier. The multi-domain bias circuit includes a coarse regulator that generates a regulated voltage based on a power supply voltage that is operable with multiple voltage levels associated with different power supply domains, a bandgap reference circuit that is powered by the regulated voltage and outputs a bandgap reference voltage, a bias voltage generator that generates multiple selectable bias voltages based on the bandgap reference voltage, and a bias voltage selector that chooses the first cascode bias voltage from amongst the selectable bias voltages.