Abstract: The purpose of the invention is to provide an accurate measurement of RF signal power transfer between a power amplifier circuit and an antenna in the presence of supply voltage variations, temperature variations and VSWR mismatch. Knowing the VSWR mismatch enables modification of a control loop for the PA and thus allows for output power adjustment in order to make the PA more efficient and robust against VSWR changes. Having an indication of power delivered to the load and the VSWR is desirable for many wireless applications especially in those applications where the PA can generate emissions that are out of band and all emissions subject to industry standards. In particular, the embodiments of the invention are applicable to wireless LANs (WLANs).

Abstract: A power amplifier circuit is disclosed having a first amplification stage and a second amplification stage. The first amplification stage is biased using a controllable current source that provides a variable bias current thereto. A control circuit is provided for controlling the variable bias current in dependence upon the supply voltage and temperature of the power amplifier circuit. The control signal varies the variable bias current in dependence upon the supply voltage varying between first and second potential, where each potential supplies sufficient potential for operation of the power amplifier circuit.