Abstract

A SiGe HBT Class-B power amplifier has been developed with a voltage-controlled variable loaf,for constant efficiency also a low power levels.The output matching network includes varactor diodes that can change the load impedance at the collector of the transistor.The load line can therefore be adjusted to provide a variable output power saturation level,shifting the peak of the efficiency to the desired power level.Constant efficiency over a wide input power range is obtained.This amplifier minimises power consumption for variable output power applications,as required in mobile communications systems.