US Patent 7276973 Automatic bias control circuit for linear power amplifiers

According to an exemplary embodiment, an amplification module includes a power amplifier configured to receive an RF input signal and provide an RF output signal. The amplification module further includes an autobias control circuit configured to receive and convert the RF output signal to a control signal. The control signal can cause the power amplifier to have a quiescent current that increases substantially linearly in response to an increase in the RF output power of the RF output signal. The autobias control circuit can include a peak detector/log converter circuit coupled to a first input of a differential amplifier, where the differential amplifier outputs the control signal. The autobias control circuit can further include a DC reference circuit coupled to a second input of the differential amplifier. The amplification module further includes an analog bias circuit coupling the control voltage to a bias input of said power amplifier.