Patent ID: 9300253
Filing Date: 2016-03-29
CPC Classification: H03F

Claim Text:
1. An amplifier comprising: a first transformer configured to have a first primary side and a first secondary side, to transform an input signal input to the first primary side to first differential signals, and to output the first differential signals from the first secondary side; a first differential amplifier configured to have an input side and an output side, the input side being coupled to the first secondary side; a second transformer configured to have a second primary side and a second secondary side, the second primary side being coupled to the output side of the first differential amplifier; a second differential amplifier coupled to the second secondary side; a third transformer configured to transform second differential signals output from the second differential amplifier to a single-ended output signal; and a first bias circuit configured to supply a first bias voltage to a first secondary coil of the first transformer, wherein the first bias circuit is configured to set the first bias voltage to a voltage greater than or equal to a first voltage on the basis of the input signal in a first operating area where power of the output signal is greater than or equal to a first power so that power-gain characteristics of the output signal become closer to characteristics where gain of the output signal becomes constant in relation to power of the output signal.