A power amplifier circuit includes a first transistor, a second transistor and a bias circuit. The first transistor has a base configured to receive a first signal. The second transistor has an emitter connecting to a collector of the first transistor and a collector configured to output a second signal. The bias circuit is coupled to the first transistor and the second transistor. The bias circuit is configured to provide a direct current (DC) voltage at the collector of the second transistor about twice a DC voltage at the collector of the first transistor. The bias circuit is configured to provide an alternating current (AC) or radio frequency (RF) voltage at the collector of the second transistor about twice an AC or RF voltage at the collector of the first transistor.

A power amplifier circuit includes a first transistor, a second transistor and a bias circuit. The first transistor has a base configured to receive a first signal. The second transistor has an emitter connecting to a collector of the first transistor and a collector configured to output a second signal. The bias circuit is coupled to the first transistor and the second transistor. The bias circuit is configured to provide a direct current (DC) voltage at the collector of the second transistor about twice a DC voltage at the collector of the first transistor. The bias circuit is configured to provide an alternating current (AC) or radio frequency (RF) voltage at the collector of the second transistor about twice an AC or RF voltage at the collector of the first transistor.

Spatial power-combining devices and, more particularly, spatial power-combining devices with improved isolation are disclosed. Spatial power-combining devices are disclosed that include a thin film resistor that is configured to provide improved signal isolation. The thin film resistor may be arranged within one or more amplifier assemblies of the spatial power-combining device to reduce signal leakage between the amplifier assemblies. The thin film resistor may be formed on a carrier substrate or the thin film resistor may supported by a surface of an amplifier assembly without a carrier substrate. Spatial power-combining devices are disclosed that include a radial arrangement of amplifier assemblies, and each amplifier assembly includes an antenna structure and a thin film resistor.

Spatial power-combining devices and, more particularly, spatial power-combining devices with improved isolation are disclosed. Spatial power-combining devices are disclosed that include a thin film resistor that is configured to provide improved signal isolation. The thin film resistor may be arranged within one or more amplifier assemblies of the spatial power-combining device to reduce signal leakage between the amplifier assemblies. The thin film resistor may be formed on a carrier substrate or the thin film resistor may supported by a surface of an amplifier assembly without a carrier substrate. Spatial power-combining devices are disclosed that include a radial arrangement of amplifier assemblies, and each amplifier assembly includes an antenna structure and a thin film resistor.

A mixer includes a load portion connected between an input terminal of a first power voltage and an output terminal of the radio frequency transmit signal and configured to adjust a magnitude of the radio frequency transmit signal, a first switching unit connected to an output terminal of the radio frequency transmit signal, and configured to perform a first switching operation in response to a plurality of local oscillation signals, and a second switching unit connected between the first switching unit and an input terminal of a second power voltage, lower than the first power voltage, and configured to perform a second switching operation in response to a plurality of baseband signals, the plurality of local oscillation signals include an I+ baseband signal, an I baseband signal, a Q+ baseband signal, and a Q baseband signal, and the second switching unit includes a first branch performing a switching operation under control of the I+ baseband signal and the Q+ baseband signal, a second branch performing a switching operation under control of the I baseband signal and the Q baseband signal, a third branch performing a switching operation under control of the Q+ baseband signal and the I baseband signal, and a fourth branch performing a switching operation under control of the Q baseband signal and the I+ baseband signal.

A high-frequency power supply circuit includes an amplifier circuit. In the amplifier circuit, one end of an inductor is connected to a direct-current power supply. One end of a switching element is connected to the other end of the inductor. A parallel capacitor is connected in parallel to the switching element. One end of an LC series circuit is connected to the one end of the switching element. A circuit capacitor is connected between the other end of the LC series circuit and the other end of the switching element. The amplifier circuit amplifies a signal having a unique frequency input to a control terminal of the switching element. The amplifier circuit outputs, to a load, a current having the frequency from a connection point between the other end of the LC series circuit and the circuit capacitor.

A variable gain amplifier circuit is disclosed. In one embodiment, an amplifier circuit includes first and second stages. Each stage includes one or more inverter pairs, with one inverter of each pair coupled to receive an inverting component of a differential signal and the other inverter of the pair coupled to receive a non-inverting component. The first stage receives a differential input signal and produces an intermediate differential signal. The second stage receives the intermediate differential signal and produces a differential output signal, the differential output signal being an amplified version of the differential input signal.

A variable gain amplifier circuit is disclosed. In one embodiment, an amplifier circuit includes first and second stages. Each stage includes one or more inverter pairs, with one inverter of each pair coupled to receive an inverting component of a differential signal and the other inverter of the pair coupled to receive a non-inverting component. The first stage receives a differential input signal and produces an intermediate differential signal. The second stage receives the intermediate differential signal and produces a differential output signal, the differential output signal being an amplified version of the differential input signal.

Herein disclosed in some embodiments is a fault detector for power amplifiers of a communication system. The fault detector can detect a portion of the power amplifiers that are in fault condition and can prevent or limit current flow to the power amplifiers in fault condition while allowing the rest of the power amplifiers to operate normally. The fault detector can further indicate which power amplifiers are in fault condition and/or the cause for the power amplifiers to be in fault condition. Based on the indication, a controller can direct communications away from the power amplifiers in fault condition and/or perform operations to correct the fault condition.

An compensation circuit for an Amplitude Modulation-Amplitude Modulation (AM-AM) of a Radio Frequency (RF) power amplifier, including: a first biasing circuit, a power amplifier, and a compensation circuit located between the first biasing circuit and the power amplifier; herein, the compensation circuit includes a diode detection circuit and a feedforward amplifier for compensating AM-AM distortion.