US Patent 9621119 Power amplifier bias signal multiplexing

A power amplifier (PA) system includes an amplifying transistor having a base, a collector, and an emitter. The PA system further includes a radio-frequency (RF) input configured to receive an RF input signal having an RF component and a DC bias component, a bias circuit coupled to the base of the amplifying transistor, and a bias tee circuit configured to receive the RF input signal and pass at least a portion of the DC component to the bias circuit and at least a portion of the RF component to the base of the amplifying transistor.