Patent ID: 9425744
Filing Date: 2016-08-23
CPC Classification: H03F,H03G

Claim Text:
1. An envelope tracking power amplifier, comprising: a multi-mode bias modulator configured to generate a variable bias voltage using a linear amplifier and a switching amplifier operating in envelope tracking mode or average power tracking mode in accordance with an operation mode control signal that determines any one of the envelope tracking mode and the average power tracking mode; and a power amplifier configured to be biased in response to the variable bias voltage, and to power amplify a radio frequency (RF) signal and output the amplified RF signal to an antenna; wherein the multi-mode bias modulator: during operation in the envelope tracking mode, drives a linear amplification bias current corresponding to an alternating current (AC) component of an envelope signal using the linear amplifier, drives a switching amplification bias current corresponding to a direct current (DC) component of the envelope signal using the switching amplifier, and generates a variable bias current by combining the linear amplification bias current with the switching amplification bias current, and during operation in the average power tracking mode, generates the variable bias current by driving the switching amplification bias current following a predetermined reference voltage using the switching amplifier; and wherein the variable bias voltage is related to an output resistance of the multi-mode bias modulator, an input resistance of the power amplifier, and the variable bias current.