A multi-way power amplifier circuit includes two baluns and a number (2N) of differential power amplifiers, where N2. Each balun generates a number (N) of corresponding differential intermediate signal pairs based on a respective to-be-amplified signal. Each differential power amplifier generates a respective differential amplified signal pair based on a respective differential intermediate signal pair. One of the baluns includes: a first transmission line and a second transmission line connected to each other; a number (N) of third transmission lines electromagnetically coupled to the first transmission line; and a number (N) of fourth transmission lines electromagnetically coupled to the second transmission line.

A Doherty amplifier used in a Z ohm based system is provided with a carrier amplifier, a peak amplifier, and an impedance transforming line for transforming the load of the carrier amplifier when an input signal is small. The impedance transforming line has a characteristic impedance lower than Z ohms and equal to the optimum load impedance of the carrier amplifier. The load of the Doherty amplifier is lower than Z ohms. A power amplifier that obtains large output power by combining output powers from a plurality of Doherty amplifiers by a power coupling circuit is constructed.

A test set system and related method are provided comprise a first direct digital synthesizer (DDS) having a balanced output configured to produce a first signal, and a second DDS having a balanced output signal configured to produce a second signal that differs from the first signal. The test set system also comprises a fully differential amplifier (FDA) having a balanced input that is connected to the balanced output of the first DDS and the balanced output of the second DDS, and a balanced output at which a combination of the first signal and the second signal is provided that suppresses even-order intermodulation products.

For broadband data communication, a data signal voltage at a signal input node can be converted to an output signal current at a signal output node. A first transistor device can contribute to the output signal current, with its transconductance or other gain reduced to accommodate larger signal swings, at which a second transistor can turn on and increase an effective resistance value of at least a portion of a gain degeneration resistor associated with the first transistor device. The second transistor can also contribute to the output signal current to help maintain or enhance an overall gain between the signal input node and the signal output node. Multiple secondary stages, push-pull arrangements, buffer amplifier configurations (which may or may not contribute to current in the gain degeneration resistor), input and output transformers, negative feedback to help reduce component variability, and frequency modification circuits or components are also described.

Systems and methods for differential antenna driving are provided. In one aspect, a front end system includes at least one power amplifier configured to receive a first transmit radio frequency signal from a baseband processor, amplify the first transmit radio frequency signal, and output the amplified first transmit radio frequency signal. The front end system further includes at least one balun configured to receive the amplified first transmit radio frequency signal. The at least one balun includes a positive output coupled to a first monopole of at least one antenna and a negative output coupled to a second monopole of the at least one antenna.

A load line impedance modulation circuit includes a magnetic circuit, an adjustable capacitance coupled to an output of the magnetic circuit, and a plurality of adjustable resistances coupled to the output of the magnetic circuit, wherein the plurality of adjustable resistances are configured to select from available output ports, an impedance presented by the load line impedance modulation circuit being adjustable dependent on at least a number of selected output ports.

There are disclosed various methods and apparatuses for amplifying a signal. In some embodiments of the method a signal is provided to an input (S) of a transconducting element (T) of an amplifier. An amplified signal is formed on the basis of the input signal by the transconducting element (T). The amplified signal is provided to an output stage. A negative conductance (R.sub.neg) in the output stage is used to adjust a gain and a noise figure of the amplifier. The amplified signal is provided via a feedback element (C.sub.fb) to another input (G) of the transconducting element (T). In some embodiments the apparatus comprises means for implementing the method.

A hybrid RF transceiver circuit comprises a first matching network, a second matching network, a first power amplifier, a second power amplifier, and a low noise amplifier. The second matching network is coupled to the first matching network and an antenna. An output port of the first power amplifier is coupled to the first matching network and the second matching network. The output port of the second power amplifier is coupled to the first matching network. The input port of the low noise amplifier is coupled to the second power amplifier and the first matching network. The output port of the low noise amplifier is coupled to a receiver circuit.

A Doherty amplifier of an embodiment includes an input terminal, an output terminal a splitter, a combiner, a carrier amplifier, a peak amplifier. The splitter is connected to the input terminal, the splitter having first and second outputs. The combiner is connected to the output terminal, the combiner having first and second inputs. The carrier amplifier includes a first input-side two-port network connected to the first output of the splitter, a first amplifier connected to an output of the first input-side two-port network, and a first output-side two-port network connected between an output of the first amplifier and the first input of the combiner. The peak amplifier includes a second input-side two-port network connected to the second output of the splitter, a second amplifier connected to the output of the second input-side two-port network, and a second output-side two-port network connected between an output of the second amplifier and the second input of the combiner. The combiner is a parallel-connected load type having a parallel connection of the output-side two-port network of the carrier amplifier and the output-side two-port network of the peak amplifier for the output terminal at a combining point. The load admittance at the combining point is expressed using a complex number.

A differential amplifier includes a pre-driver stage, an input balun, a matching network, a differential transistor pair, a bias network and an output balun. An output terminal of the pre-driver stage is connected to an input terminal of the input balun. An output terminal of the input balun is connected to the matching network. An output terminal of the matching network is connected to an input terminal of the differential transistor pair and to the bias network. An output terminal of the differential transistor pair is connected to the output balun. A single-turn laminated transformer is used as the input balun of the present invention, and the output balun is of a structure having an inner full frame and an outer half frame, thereby making the differential amplifier have small occupation area, low loss, high operating frequency and high power amplification efficiency.