An amplification circuit includes a first switching circuit that includes input terminals and first and second output terminals and that puts the second output terminal into an open state with respect to the input terminals while selectively putting the first output terminal into a state of being connected to any of the input terminals or selectively puts the second output terminal into a state of being connected to any of input terminals while putting the first output terminal into a state of being open with respect to the input terminals; a matching network that is connected to the first output terminal; an amplifier that is connected to an output side of the matching network; a second switching circuit that is connected to an output side of the amplifier; and a bypass path that electrically connects the second output terminal and an output terminal of the second switching circuit. The amplifier is a variable-gain amplifier.

A ultra-compact coupler designed to sample the actual output power of a power amplifier and which is VSWR insensitive, such that reflected power is essentially not coupled to a detector circuit and only forward power is detected and processed. In a first embodiment, a coupler is situated between the final amplifier stage of a power amplifier and an output impedance matching network, and is specially configured for operation in a low impedance environment in conjunction with a detector circuit, thereby substantially reducing the areal size of the coupler. In a second embodiment, a coupler is integrated within an output impedance matching network coupled to the final amplifier stage of a power amplifier so as to share an inductor between the coupler and the output impedance matching network, thereby further substantially reducing the areal size of the coupler.

A ultra-compact coupler designed to sample the actual output power of a power amplifier and which is VSWR insensitive, such that reflected power is essentially not coupled to a detector circuit and only forward power is detected and processed. In a first embodiment, a coupler is situated between the final amplifier stage of a power amplifier and an output impedance matching network, and is specially configured for operation in a low impedance environment in conjunction with a detector circuit, thereby substantially reducing the areal size of the coupler. In a second embodiment, a coupler is integrated within an output impedance matching network coupled to the final amplifier stage of a power amplifier so as to share an inductor between the coupler and the output impedance matching network, thereby further substantially reducing the areal size of the coupler.

Multi-band power amplification system having enhanced efficiency through elimination of band selection switch. In some embodiments, a power amplification system can include a plurality of power amplifiers (PAs), with each PA being configured to receive and amplify a radio-frequency (RF) signal in a frequency band. The power amplification system can further include an output filter coupled to each of the PAs by a separate output path such that the power amplification system is substantially free of a band selection switch between the plurality of PAs and their corresponding output filters. Each PA can be further configured to drive approximately a characteristic load impedance of the corresponding output filter by, for example, the PA being operated with a high-voltage (HV) supply.

Multi-band power amplification system having enhanced efficiency through elimination of band selection switch. In some embodiments, a power amplification system can include a plurality of power amplifiers (PAs), with each PA being configured to receive and amplify a radio-frequency (RF) signal in a frequency band. The power amplification system can further include an output filter coupled to each of the PAs by a separate output path such that the power amplification system is substantially free of a band selection switch between the plurality of PAs and their corresponding output filters. Each PA can be further configured to drive approximately a characteristic load impedance of the corresponding output filter by, for example, the PA being operated with a high-voltage (HV) supply.

A power amplifier circuit comprising a transistor for receiving a signal to be amplified at an input and for outputting an amplified signal at an output; a modulated power supply connected to the transistor output; and a resistive element connected at the transistor output such that a low impedance is maintained at the transistor output across a range of operational frequencies.

A power amplifier circuit comprising a transistor for receiving a signal to be amplified at an input and for outputting an amplified signal at an output; a modulated power supply connected to the transistor output; and a resistive element connected at the transistor output such that a low impedance is maintained at the transistor output across a range of operational frequencies.

Provided is a power amplification circuit that includes: an amplifier that amplifies an input signal and outputs an amplified signal; a first bias circuit that supplies a first bias current or voltage to the amplifier; a second bias circuit that supplies a second bias current or voltage to the amplifier; a first control circuit that controls the first bias current or voltage; and a second control circuit that controls the second bias current or voltage. The current supplying capacity of the first bias circuit is different from the current supplying capacity of the second bias circuit.

Provided is a power amplification circuit that includes: an amplifier that amplifies an input signal and outputs an amplified signal; a first bias circuit that supplies a first bias current or voltage to the amplifier; a second bias circuit that supplies a second bias current or voltage to the amplifier; a first control circuit that controls the first bias current or voltage; and a second control circuit that controls the second bias current or voltage. The current supplying capacity of the first bias circuit is different from the current supplying capacity of the second bias circuit.

Provided is a power amplification module that includes: a first amplification circuit that amplifies a first signal and outputs the amplified first signal as a second signal; a second amplification circuit that amplifies the second signal and outputs the amplified second signal as a third signal; and a feedback circuit that re-inputs/feeds back the second signal outputted from the first amplification circuit to the first amplification circuit as the first signal. The operation of the first amplification circuit is halted and the first signal passes through the feedback circuit and is outputted as the second signal at the time of a low power output mode.