Power amplifier modules including bipolar transistor with grading and related systems, devices, and methods

A power amplifier module comprising:

• a packaging substrate configured to receive a plurality of components;
• a first die mounted on the packaging substrate, the first die including a power amplifier including a GaAs bipolar transistor having a collector, a base, and an emitter, the collector having a doping concentration of at least about 3×1016 cm−3 at an interface with the base, the collector also having a grading in which doping concentration increases away from the base, and the first die further including a passive component having an electrical property that depends on a condition of the first die;
• and
• a second die mounted on the packaging substrate and in communication with the first die, the second die including a bias circuit configured to generate a bias signal based at least partly on an indication of the electrical property of the passive component of the first die and to provide the bias signal to the power amplifier.