Patent ID: 7439806
Filing Date: 2008-10-21
Classification: H03F

Abstract:
1. A bias control circuit for a radio frequency (RF) amplifier having an output device for providing an output signal to a load and a driver device for providing a drive signal to the output device, the bias control circuit comprising: a voltage reference circuit adapted to receive a supply voltage and to produce therefrom a reference voltage; a current mirror circuit adapted to receive the reference voltage and to provide a driver device bias current for the driver device and an output device bias current for the output device; an adaptive mode control circuit adapted to receive a supply voltage and in response to a voltage level of the supply voltage, to provide to the current mirror circuit a first mode control signal indicating one of a high power mode and a low power mode, the first mode control signal adjusting the output device bias current provided by the current mirror circuit to the output device for selectively turning on the output device in the high power mode and turning off the output device in the low power mode; and a driver stage control circuit adapted to receive a second mode control signal indicating one of the high power mode and the low power mode, and in response to the second mode control signal indicating the low power mode, to receive a bias adjust voltage and in response thereto to provide a driver device bias current adjust signal to the current mirror circuit for adjusting the driver device bias current.