Group III nitride based depletion mode differential amplifiers and related RF transistor amplifier circuits

A radio frequency (“RF”) transistor amplifier circuit, comprising:

• a Group III nitride based RF transistor amplifier having a gate terminal;
• a Group III nitride based self-bias circuit that includes a first Group III nitride based depletion mode high electron mobility transistor, the Group III nitride based self-bias circuit configured to generate a bias voltage;
• and
• a Group III nitride based depletion mode differential amplifier that is configured to generate an inverted bias voltage from the bias voltage and to apply the inverted bias voltage to the gate terminal of the Group III nitride based RF transistor amplifier,
• wherein the Group III nitride based depletion mode differential amplifier comprises a differential amplifier stage, a level shifter stage, an output buffer stage, and a current source stage, and
• wherein the Group III nitride based RF transistor amplifier, the Group III nitride based self-bias circuit and the Group III nitride based depletion mode differential amplifier are all implemented in a single die.