The RF amplifier bias controller can generate a regulation of the drain voltage and actively adjust the gate voltage of the external amplifier, thereby achieving a constant bias current. It can be used to provide appropriate bias for enhancement and depletion type amplifiers in the A-class region (with specified drain voltage (VDRAIN)). These devices achieve excellent bias stability in terms of voltage, temperature and process variations, avoiding the calibration process required to prevent RF performance degradation caused by this.