Patent ID: 8587377
Filing Date: 2013-11-19
Classification: H03F

Abstract:
1. A power amplifier system comprising: a power amplifier configured to amplify a radio frequency (RF) signal; and a bias control circuit configured to generate a bias current for the power amplifier, the bias control circuit further configured to receive an envelope of the RF signal and to change an amplitude of the bias current based at least in part on the envelope, the bias control circuit including a converter for generating a reference signal using the envelope and a current mirror configured to receive the reference signal from the converter and to use the reference signal to generate the bias current, the reference signal having a shaping that, changes in relation to the envelope, the current mirror including a field-effect transistor having a gate, a source and a drain and a bipolar transistor having an emitter, a base and a collector, the gate of the field-effect transistor electrically connected to collector of the bipolar transistor and the source of the field-effect transistor electrically connected to the base of the bipolar transistor, the collector of the bipolar transistor and the gate of the field-effect transistor configured to receive the reference signal from the converter, and the source of the field-effect transistor configured to generate the bias current.