Apparatus and methods for power amplifier biasing

A packaged module comprising:

• a package substrate;
• and
• an integrated circuit attached to the package substrate, the integrated circuit including a reference current source configured to generate a reference current, a bipolar reference transistor, and a transimpedance amplifier configured to amplify a difference between a collector current of the bipolar reference transistor and the reference current, and to provide a base bias voltage to a base of the bipolar reference transistor, the integrated circuit further including a power amplifier configured to generate a radio frequency output signal based on amplifying a radio frequency input signal, the power amplifier including a bipolar power amplifier transistor including a base biased by the base bias voltage such that the power amplifier has a substantially flat gain response versus time, the transimpedance amplifier further configured to receive an enable signal operable to selectively pulse the radio frequency output signal of the power amplifier.